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31 Days Before
Your CCNA Exam
Scott Bennett

Cisco Press

800 East 96th Street

Indianapolis, Indiana 46240 USA

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31 Days Before Your CCNA Exam
Scott Bennett
Copyright © 2007 Cisco Systems, Inc.
Published by:
Cisco Press
800 East 96th Street
Indianapolis, IN 46240 USA
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any
means, electronic or mechanical, including photocopying, recording, or by any information storage
and retrieval system, without written permission from the publisher, except for the inclusion of
brief quotations in a review.
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
First Printing August 2006
Library of Congress Cataloging-in-Publication Number: 2005938126
ISBN: 1-58713-174-9

Warning and Disclaimer
This book is designed to provide information about the Cisco Networking Academy Program CCNA
curriculum. Every effort has been made to make this book as complete and as accurate as possible,
but no warranty or fitness is implied.
The information is provided on an “as is” basis. The authors, Cisco Press, and Cisco Systems, Inc.,
shall have neither liability nor responsibility to any person or entity with respect to any loss or damages
arising from the information contained in this book or from the use of the discs or programs that may
accompany it.
The opinions expressed in this book belong to the author and are not necessarily those of
Cisco Systems, Inc.

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Feedback Information
At Cisco Press, our goal is to create in-depth technical books of the highest quality and value. Each
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Readers’ feedback is a natural continuation of this process. If you have any comments regarding
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Trademark Acknowledgments
All terms mentioned in this book that are known to be trademarks or service marks have been
appropriately capitalized. Cisco Press or Cisco Systems, Inc. cannot attest to the accuracy of this
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About the Author
Scott Bennett earned his CCNA, CCAI, and CompTia A+ while working and teaching in the technology industry. After graduating from Gonzaga University, Scott went on to work with Qwest
eBits, providing network support and training to businesses throughout Idaho. His current position
as a Cisco Networking Academy instructor for the Capital Center High School Technology
Institute and Portland Community College provided the ideas and inspiration for this book.

About the Technical Reviewers
Mark R. Anderson, CCNA/CCNP, has been the lead Cisco Network Academy faculty at Mesa
Community College in Mesa, Arizona since 1999. His 25+ years in the IT industry has given him
invaluable experience in preparing and passing many technical certification exams, such as CCNA,
CCNP, MCSE, and MCNE. As a teacher, his passion has been to help students develop and expand
their professional growth in the IT industry. He earned a Bachelor of Education from Pacific Lutheran
University and a Master of Liberal Studies in Information Networking and Telecommunication
from Fort Hays State University. Mark lives in Gilbert, Arizona with Sandra, his wife of 35 years,
and nearby adult children, Clint, Jennifer, and Trisha.
Glenn Wright, CCNA, CCAI, is the co-director of the Cisco Academy Training Center (CATC) in
Ft. Worth, Texas. He has been involved in many aspects of the Cisco Networking Academy Program
since 1999. He serves the Academy Program as an instructor and supports academies in Texas,
Louisiana, Oklahoma, and Arkansas. Glenn has also worked with the Academy Quality Assurance
Team, reviewing and editing Academy curriculum and assessment.

Angie. Johnny. and to Pam and George.00_1587131749_fm.qxd vi 7/28/06 8:52 AM Page vi 31 Days Before Your CCNA Exam Dedication To Grandpa Matt. my loving and supportive parents. Monnie. my energetic and caring siblings. for creating my beloved beautiful wife. and Christi. Jimmy. . Jim and Shari.

professionalism. Jeff Wirtzfeld for his support. for teaching me the real meaning of the words endurance and dedication. I want to thank Coach Dan Gehn. I also want to thank Matt Schoenfeldt for his continued and contagious eccentric passion about all things technical. Pete Craemer and David Gilde for their encouragement as fellow educators at the Capital Center High School. Thank you for this remarkable experience and opportunity. and attention to detail while editing the text. thank you for your patience. supervision. and ability to turn an idea into a proposal amaze me. Chris Cleveland. Thank you to Dayna Isley for the innumerable improvements you contributed to the book and your positive encouragement. I would like to thank Trevor Hardcastle and Weiping He for keeping me on my toes as a teacher and in hopes that they might include my name in all of their future books. .qxd 7/28/06 8:52 AM Page vii vii Acknowledgments First. Lastly. and Gary Schlienkofer for his aid with our Local Cisco Networking Academy. I greatly appreciate Allan Johnson’s willingness to use a draft of the text in his CCNA review class and provide advice and assistance. wealth of knowledge. I want to thank Mary Beth Ray for her help in this process from start to finish. I also want to thank my friend Peter Buss for providing the perspective and empathy of a seasoned network administrator. and friendship at Qwest. thank you for pointing me in the right direction with the initial chapter and contributing the OSI model pneumonic device.00_1587131749_fm. Her enthusiasm. Thank you to the entire Cisco Press team that worked behind the scenes to help create this book. and Professor Steven Gillick for his enthusiasm in the classroom and generous distribution of red ink on my papers. Mark Anderson and Glenn Wright.

00_1587131749_fm. and Gateway Addresses on Routers and Hosts 99 Day 15: Configure a Router for Additional Administrative Functionality Day 14: Configure a Switch with VLANs and Interswitch Communication Day 13: Implement a LAN 121 105 113 . Subnet Masks.qxd viii 7/28/06 8:52 AM Page viii 31 Days Before Your CCNA Exam Contents at a Glance Part I : 31-24 Days Before the Exam—Technology 1 Day 31: Describe Network Communications Using Layered Models Day 30: Describe the Spanning Tree Process 3 11 Day 29: Compare and Contrast Key Characteristics of LAN Environments Day 28: Evaluate the Characteristics of Routing Protocols 15 19 Day 27: Evaluate the TCP/IP Communication Process and Its Associated Protocols 27 Day 26: Describe the Components of Network Devices Day 25: Evaluate Rules for Packet Control 35 39 Day 24: Evaluate Key Characteristics of WANs 43 Part II: 23–18 Days Before the Exam—Planning and Design Day 23: Design a Simple LAN Using Cisco Technology 47 49 Day 22: Design an IP Addressing Scheme to Meet Design Requirements 57 Day 21: Select an Appropriate Routing Protocol Based on User Requirements 63 Day 20: Design a Simple Internetwork Using Cisco Technology Day 19: Develop an Access List to Meet User Specifications 69 73 Day 18: Choose WAN Services to Meet Customer Requirements 77 Part III: 17–9 Days Before the Exam—Implementation and Operation 87 Day 17: Configure Routing Protocols Given User Requirements 89 Day 16: Configure IP Addresses.

00_1587131749_fm.qxd 7/28/06 8:52 AM Page ix ix Day 12: Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives) 125 Day 11: Perform an Initial Configuration on a Router and Perform an Initial Configuration on a Switch (Two Objectives) 133 Day 10: Implement an Access List 141 Day 9: Implement Simple WAN Protocols 145 Part IV: 8–1 Day(s) Before the Exam—Troubleshooting 153 Day 8: Utilize the OSI Model as a Guide for Systematic Troubleshooting Day 7: Perform LAN and VLAN Troubleshooting Day 6: Troubleshoot Routing Protocols 159 163 Day 5: Troubleshoot IP Addressing and Host Configuration 167 Day 4: Troubleshoot a Device as Part of a Working Network Day 3: Troubleshoot an Access List 175 Day 2: Perform Simple WAN Troubleshooting 177 Day 1: Key Points from Each Day for Relaxed Skimming Part V: Exam Day and Post-Exam Information Exam Day: Becoming a CCNA 205 Post-Exam Information: After the CCNA Index: 211 171 207 181 203 155 .

Module 9 5 CCNA 1. Module 5 17 Summary Your Notes 18 18 Day 28: Evaluate the Characteristics of Routing Protocols CCNA 2. Module 4 16 CCNA 3.00_1587131749_fm. Module 2 3 CCNA 1. Module 2 15 CCNA 1. Module 1 16 CCNA 3.qxd x 7/28/06 8:52 AM Page x 31 Days Before Your CCNA Exam Contents Part I : 31-24 Days Before the Exam—Technology 1 Day 31: Describe Network Communications Using Layered Models CCNA 1. Module 6 19 CCNA 2. Module 6 15 CCNA 2. Module 3 23 Summary Your Notes 25 26 19 15 . Module 7 11 Summary Your Notes 3 11 12 13 Day 29: Compare and Contrast Key Characteristics of LAN Environments CCNA 1. Module 2 22 CCNA 3. Module 7 21 CCNA 3. Module 1 22 CCNA 3. Module 8 11 CCNA 3. Module 11 CCNA 3. Module 5 Summary Your Notes 6 9 9 10 Day 30: Describe the Spanning Tree Process CCNA 1. Module 6 5 CCNA 1.

Module 1 43 CCNA 4. Module 4 45 CCNA 4. Module 8 CCNA 2. Module 6 CCNA 2. Module 2 28 CCNA 1. Module 1 35 CCNA 2. Module 9 28 CCNA 1. Module 2 36 Summary Your Notes 37 38 Day 25: Evaluate Rules for Packet Control CCNA 1. Module 2 43 CCNA 2. Module 2 43 CCNA 4. Module 1 27 CCNA 1. Module 3 45 CCNA 4.00_1587131749_fm. Module 11 CCNA 2. Module 10 Summary Your Notes 31 32 32 32 33 34 Day 26: Describe the Components of Network Devices CCNA 2. Module 11 Summary Your Notes 39 39 39 41 42 Day 24: Evaluate Key Characteristics of WANs CCNA 1. Module 10 CCNA 1. Module 5 45 Summary Your Notes 46 46 43 35 .qxd 7/28/06 8:52 AM Page xi xi Day 27: Evaluate the TCP/IP Communication Process and Its Associated Protocols 27 CCNA 1.

Module 5 54 Your Notes 49 53 CCNA 2. Module 8 51 CCNA 1. Module 10 63 CCNA 2. Module 6 64 CCNA 3. Module 3 66 Summary Your Notes 47 67 68 Day 20: Design a Simple Internetwork Using Cisco Technology CCNA 1. Module 8 70 69 57 . Module 1 61 Summary Your Notes 62 62 Day 21: Select an Appropriate Routing Protocol Based on User Requirements 63 CCNA 1. Module 1 57 CCNA 1. Module 2 69 CCNA 1. Module 9 57 CCNA 1. Module 1 60 CCNA 4. Module 5 50 CCNA 1. Module 9 52 CCNA 1. Module 1 65 CCNA 3. Module 10 54 CCNA 3. Module 2 49 CCNA 1.00_1587131749_fm. Module 1 Summary 55 56 Day 22: Design an IP Addressing Scheme to Meet Design Requirements CCNA 1. Module 10 58 CCNA 3. Module 2 65 CCNA 3.qxd xii 7/28/06 8:52 AM Page xii 31 Days Before Your CCNA Exam Part II: 23–18 Days Before the Exam—Planning and Design Day 23: Design a Simple LAN Using Cisco Technology CCNA 1.

qxd 7/28/06 8:52 AM Page xiii xiii CCNA 3. Module 2 71 Summary Your Notes 72 72 Day 19: Develop an Access List to Meet User Specifications CCNA 2. Module 3 96 Summary Your Notes 97 98 89 . Module 1 70 CCNA 4. Module 2 78 CCNA 4. Module 5 77 CCNA 2. Module 3 81 CCNA 4. Module 8 70 CCNA 4.00_1587131749_fm. Module 5 85 Summary Your Notes 77 86 86 Part III: 17–9 Days Before the Exam—Implementation and Operation 87 Day 17: Configure Routing Protocols Given User Requirements CCNA 2. Module 1 89 CCNA 2. Module 6 89 CCNA 2. Module 4 83 CCNA 4. Module 2 77 CCNA 1. Module 2 93 CCNA 3. Module 1 78 CCNA 4. Module 11 Summary Your Notes 73 73 74 75 Day 18: Choose WAN Services to Meet Customer Requirements CCNA 1. Module 7 90 CCNA 3. Module 1 92 CCNA 3.

Module 2 102 Summary Your Notes 103 104 Day 15: Configure a Router for Additional Administrative Functionality CCNA 2. Module 7 124 Your Notes 113 118 Day 13: Implement a LAN Summary 105 121 124 124 Day 12: Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives) 125 CCNA 3. Module 4 122 CCNA 1. Module 6 111 Summary Your Notes 112 112 Day 14: Configure a Switch with VLANs and Interswitch Communication CCNA 3. Subnet Masks. Module 1 107 CCNA 4. and Gateway Addresses on Routers and Hosts 99 CCNA 1. Module 4 125 CCNA 3. Module 1 102 CCNA 3. Module 8 113 CCNA 3. Module 3 126 . Module 5 123 CCNA 1. Module 9 115 Summary Your Notes 119 CCNA 1. Module 2 121 CCNA 1. Module 3 99 CCNA 3. Module 3 105 CCNA 4. Module 5 126 CCNA 2.qxd xiv 7/28/06 8:52 AM Page xiv 31 Days Before Your CCNA Exam Day 16: Configure IP Addresses. Module 1 99 CCNA 1.00_1587131749_fm. Module 9 99 CCNA 2.

Module 11 Summary Your Notes 141 141 143 144 Day 9: Implement Simple WAN Protocols CCNA 2. Module 10 CCNA 4. Module 3 134 CCNA 3. Module 6 135 Summary Your Notes 138 139 Day 10: Implement an Access List CCNA 2. Module 1 145 CCNA 4. Module 5 Summary Your Notes 127 131 131 Day 11: Perform an Initial Configuration on a Router and Perform an Initial Configuration on a Switch (Two Objectives) 133 CCNA 2. Module 9 155 CCNA 2. Module 3 145 CCNA 4. Module 2 155 CCNA 2.qxd 7/28/06 8:52 AM Page xv xv CCNA 2. Module 5 149 Summary Your Notes 145 151 152 Part IV: 8–1 Day(s) Before the Exam—Troubleshooting 153 Day 8: Utilize the OSI Model as a Guide for Systematic Troubleshooting CCNA 1. Module 4 146 CCNA 4. Module 6 Summary Your Notes 157 158 157 157 155 . Module 8 155 CCNA 2. Module 2 133 CCNA 2.00_1587131749_fm.

Module 11 Summary Your Notes 167 175 176 175 175 171 . Module 4 159 CCNA 2. Module 5 171 CCNA 2. Module 4 167 CCNA 2. Module 2 164 CCNA 3. Module 7 163 CCNA 2. Module 3 165 Summary Your Notes 159 163 166 166 Day 5: Troubleshoot IP Addressing and Host Configuration CCNA 2. Module 9 160 CCNA 3. Module 4 171 CCNA 2. Module 9 163 CCNA 3. Module 5 160 CCNA 2. Module 1 164 CCNA 3. Module 8 161 Summary Your Notes 161 162 Day 6: Troubleshoot Routing Protocols CCNA 2. Module 9 172 Summary Your Notes 172 173 Day 3: Troubleshoot an Access List CCNA 2.00_1587131749_fm. Module 2 171 CCNA 2. Module 1 171 CCNA 2. Module 9 168 Summary Your Notes 168 169 Day 4: Troubleshoot a Device as Part of a Working Network CCNA 1.qxd xvi 7/28/06 8:52 AM Page xvi 31 Days Before Your CCNA Exam Day 7: Perform LAN and VLAN Troubleshooting CCNA 2.

Module 4 177 CCNA 4. Module 5 178 Summary 177 178 Your Notes 179 Day 1: Key Points from Each Day for Relaxed Skimming Day 31 181 Day 30 182 Day 29 183 Day 28 183 Day 27 184 Day 26 185 Day 25 185 Day 24 186 Day 23 186 Day 22 187 Day 21 188 Day 20 188 Day 19 189 Day 18 189 Day 17 190 Day 16 191 Day 15 192 Day 14 193 Day 13 194 Day 12 194 Day 11 196 Day 10 197 Day 9 197 Day 8 199 181 .qxd 7/28/06 8:52 AM Page xvii xvii Day 2: Perform Simple WAN Troubleshooting CCNA 4. Module 3 177 CCNA 4.00_1587131749_fm.

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■ Braces { } indicate a required choice. . ■ A command that does not fit on one line due to the constraints of the book’s width will continue on the next line with a two-space indent. In actual configuration examples and output (not general command syntax). ■ Braces within brackets [{ }] indicate a required choice within an optional element. ■ Italics indicate arguments for which you supply actual values.00_1587131749_fm. boldface indicates commands that are manually input by the user (such as a show command). The Command Reference describes these conventions as follows: ■ Boldface indicates commands and keywords that are entered literally as shown. ■ Square brackets [ ] indicate optional elements.qxd 7/28/06 8:52 AM Page xix xix Icons Used in This Book Communication Server PC PC with Software Terminal File Server Sun Workstation Macintosh Access Server ISDN/Frame Relay Switch Cisco Works Workstation ATM Switch Modem Token Ring Token Ring Printer Laptop Web Server IBM Mainframe Front End Processor Cluster Controller Multilayer Switch FDDI Gateway Router Network Cloud Bridge Line: Ethernet Hub Line: Serial DSU/CSU DSU/CSU FDDI Catalyst Switch Line: Switched Serial Command Syntax Conventions The conventions used to present command syntax in this book are the same conventions used in the IOS Command Reference. ■ Vertical bars (|) separate alternative. mutually exclusive elements.

Time to take the CCNA 640-801 exam and make your knowledge official. Second Edition (ISBN 1587200791) by Jim Doherty and Eric Rivard.qxd xx 7/28/06 8:52 AM Page xx 31 Days Before Your CCNA Exam Introduction 31 Days Before Your CCNA Exam represents the end of your adventure through the Cisco Networking Academy CCNA courses 1–4. Each day in the book uses the following formats to review the Networking Academy online curriculum: ■ Short summaries of key concepts and definitions from the curriculum with a reference to the Networking Academy online module section number ■ Tables and figures to help you recognize topics that you covered during your Networking Academy studies ■ No-frills Cisco IOS software command-line examples to jog your memory about the configurations and lab exercises that relate to each CCNA objective ■ References for further study and practice testing with the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. This book can also provide instructors and students with a concise way to review all four courses at the end of a CCNA 4 class and add a little personality and a new angle to the Academy curriculum. . Use this book and its organized course of study to take the guesswork out of your comprehensive academy review for the CCNA.00_1587131749_fm. You owe it to yourself to complete your academy studies with a CCNA certification. This book essentially offers a stepping-stone in what might otherwise feel like a big leap between the Cisco Networking Academy curriculum and the CCNA exam. Each day breaks down each exam topic into a manageable bite using short summaries from the online curriculum and a conversational tone to make your study time more enjoyable. You will read short summaries of sections from the Networking Academy online curriculum as they relate to each of the exam topics for the CCNA. This book also outlines the format of the CCNA exam and the registration requirements you must fulfill to take the CCNA exam. You can use this book to fit CCNA studies into an otherwise busy schedule with a daily timeline and clear references to other CCNA study materials. exam #640-801). Who Should Read This Book? The primary audience for this book is anyone teaching or enrolled in the Cisco Networking Academy CCNA 4 WAN Technologies course or recent graduates of the Cisco Networking Academy CCNA curriculum who have not yet passed the CCNA exam. Goals and Methods The main goal of this book is to provide you with a clear map from the Cisco Networking Academy Program online curriculum to the CCNA exam.

The book counts down starting with Day 31 and continues through exam day to provide post-test information. implementation and operation. Use the checklist to map out your studies for the CCNA exam. ■ Capture video lessons of yourself and watch them. Each day is titled with the CCNA exam objective. Study Tips As you begin studying for the CCNA exam. you need to inject yourself into this information. Second Edition (ISBN 1587200791). planning and design. Each subheading provides the module and section from the Networking Academy course and then provides a brief description of topics related to that day’s exam objective. Look for daily reading quizzes and activities online. The checklist highlights important tasks and deadlines leading up to your exam. then you do not know it. you may find it helpful to buy a whiteboard. or CCNA 4). and tackle the suggested readings and practice exams for each day. The 31 days are broken into the four categories for the CCNA 640-801 exam: technology. Visit the book’s product page at www. The following activities could also help you to prepare: ■ Podcast audio discussions about CCNA topics. . exam #640-801). CCNA 3. ■ Donate a set amount for every hour that you study to a children’s hospital.ciscopress. You can also put a red X on each day you complete. Your desire to get a CCNA and understand these concepts will shine through on test day. CCNA 2.qxd 7/28/06 12:27 PM Page xxi xxi How This Book Is Organized After you read through the instructions provided later in this introduction for registering for the CCNA exam. and each heading identifies the Networking Academy course (CCNA 1. and troubleshooting. If you cannot explain and diagram an objective. The calendar provides a visual for the time you can dedicate to each CCNA exam objective. Get a dry erase marker and fill the room with that awful scent while you diagram and teach each of the concepts to yourself. time. The real test happens when your boss asks you to explain a networking concept or to defend your suggestion in a meeting. the books starts by breaking up the exam topics by day.00_1587131749_fm. Teach out loud. ■ Blog what you are learning. you will find a calendar and checklist that you can tear out and use during your exam preparation. and location of your CCNA exam. Ask friends to sponsor you. Teach whoever will listen. ■ Get a copy of CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.com/title/1587131749 to access the content. Use the calendar to enter each actual date beside the countdown day and the exact day. More important than anything. like those movie montages where the lead character is preparing for something very important. At the end of the book.

.00_1587131749_fm. connect. but you need this category to fix networks affected by natural disasters. Although Cisco outlines general exam topics. and environment will build your confidence and reduce the chance of any unpleasant surprises on exam day. hardware issues. Exam Topics The topics of the CCNA 640-801 exam focus around the following four key categories: ■ Technology—The topics in this category relate to the theory and concepts behind networks. ■ Implementation and operation—This category is where you prove that you can actually connect and configure a network. The exam topics provided by Cisco and included in this book are a general framework for exam preparation. and troubleshoot networks. compare.com and look at the latest exam topics. including layered models as well as network process descriptions. configure. format.qxd xxii 7/28/06 8:52 AM Page xxii 31 Days Before Your CCNA Exam Getting to Know the CCNA Exam The CCNA 640-801 tests your ability to describe. but also knowing the testing process. ■ Troubleshooting—As a Cisco Networking Academy student. Just knowing the information will help you on the exam. ■ Planning and design—This category asks you to organize the concepts of networking into real-world examples. it is possible that not all topics will appear on the CCNA exam and that topics that are not specifically listed may appear on the exam. You can navigate to CCNA information through the Learning and Events link. each day represents a CCNA exam topic and each day maps the information you have learned in the Cisco Networking Academy Curriculum to a CCNA exam topic. In this book. Be sure to check Cisco. Each category includes general exam topics. and the occasional malfunctioning keyboard during IP address configuration. your networks are always perfect.

These questions are similar to the drag-and-drop Interactive Media Activities in the Academy online curriculum. Cisco. and a bottom window pane contains a router simulation that you can use to answer the questions. Simlet A top window pane contains questions. Testlet You see an upper pane and lower pane in the main window for this type of task. Step 2. Click the Certification Exam Information link. Step 4. Table I-1 CCNA Question Types Question Type Description Multiple-choice single answer You choose one and only one option for an answer. Visit http://www. The following steps allow you to access this tutorial: Step 1. Sometimes there will be more than one text box. Step 5. identify the question types that will take you longer to complete so that you can manage your time on exam day. Step 3. Click the Learning and Events link. Table I-1 outlines each type of question that you might encounter on the exam. Remember that not all commands are supported in these simulations and that you can view the topology of the network in some simulations. and the lower pane contains multiple-choice questions with single and multiple answers. . On the right side. The question itself will tell you how many answers you must select.com has an exam tutorial that simulates each of these types of questions.cisco. The upper pane contains a scenario.com. you are allowed 90 minutes to answer 55–65 questions. Fill-in-the-blank You click a text box and then type the answer. Click the Career Certifications and Paths link. you can scroll through the scenario and select questions. Click the Certification Exam Tutorial link.00_1587131749_fm. Multiple-choice multiple answer You choose more than one answer. You see the actual problem at the top and the directions on the left. Drag-and-drop You drag and release objects to visually arrange the answer on the page. As you work through the exam tutorial. Simulations This task is similar to the e-Labs that cover configurations.qxd 7/28/06 8:52 AM Page xxiii xxiii Exam Format For the CCNA exam.

qxd xxiv 7/28/06 8:52 AM Page xxiv 31 Days Before Your CCNA Exam Your Path to the CCNA As a Cisco Networking Academy student. you should plan to pass the CCNA voucher exam and take advantage of the practice and skills exams available through the Cisco Academy web site. Your voucher will be redeemable for a discount on the CCNA exam at a Prometric or Pearson VUE testing center. single-answer and multiple-choice.00_1587131749_fm. The default duration of the exam is 75 minutes. and the exam includes multiple-choice. you will be able to request a voucher from your Cisco Academy home page. If you pass the voucher exam and have successfully completed all final exams for The Cisco Networking Academy CCNA 1 through CCNA 4 with a 70 percent or better in the first attempt. CCNA 640-801 Certification Practice Exams 1 and 2 The CCNA Certification Practice Exams 1 and 2 have between 55 and 60 questions. you can register to take the CCNA exam. You must be enrolled in a CCNA 4 class and request that your instructor enable these practice exams in the Cisco Academy online assessment system. and you are allowed 120 minutes on each exam by default. You can take these exams up to ten times each.” The specific percentage that indicates “voucher eligible” is different for each form. Before you complete CCNA 4. . you have a unique opportunity to integrate your final days of the study with preparation for the CCNA exam. multiple-answer questions. CCNA 640-801 Voucher Exam Your instructor can activate and proctor this exam for you through the Cisco Academy web site during the CCNA 4 course. It is important to schedule the following three exams with your Academy instructor in order to be best prepared for the CCNA: ■ CCNA 640-801 Voucher Exam ■ CCNA 640-801 Certification Practice Exam 1 ■ CCNA 640-801 Certification Practice Exam 2 After completing these exams. You have three attempts (each a different form of the exam) to complete with a score of “voucher eligible. The discount percentage varies by region and testing center.

If you had an account with a testing partner before you began with the Academy.com/cisco Thomson Prometric 1-800-829-6387 option 1 then option 4 http://securereg3. it is important to ensure that your profile is updated with your Academy information for the Academy voucher before you register. Sign up as soon as you have your voucher.00_1587131749_fm. The process and available test times will vary based on how and with whom you decide to register. You can contact the testing partners in Table I-3 to register for an exam.com There is no better motivation for study than an actual test date. Table I-2 Personal Information for CCNA 640-801 Exam Registration Item Notes Legal name Social Security or passport number Cisco certification ID or test ID Cisco Academy username Required for your voucher Cisco Academy ID number Required for your voucher Company name Valid e-mail address Voucher number Required for your voucher Method of payment Typically a credit card You can register for an exam up to six weeks in advance or as late as the day before the exam.prometric. Table I-3 Test Delivery Partners Testing Partner Phone Number Website Pearson VUE 1-800-829-6387 option 1 then option 4 http://www. . you need to gather the information outlined in Table I-2 to register for the CCNA 640-801 exam.vue.qxd 7/28/06 8:52 AM Page xxv xxv Registering for the CCNA Exam Once you have taken these exams and redeemed your voucher.

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01_1587131749_Pt1.qxd 7/28/06 8:52 AM Page 1 Part I 31-24 Days Before the Exam— Technology Day 31: Describe Network Communications Using Layered Models Day 30: Describe the Spanning Tree Process Day 29: Compare and Contrast Key Characteristics of LAN Environments Day 28: Evaluate the Characteristics of Routing Protocols Day 27: Evaluate the TCP/IP Communication Process and Its Associated Protocols Day 26: Describe the Components of Network Devices Day 25: Evaluate Rules for Packet Control Day 24: Evaluate Key Characteristics of WANs .

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3—Initially. shapeless jelly.4 and 2. Table 31-1 describes each layer of the OSI model. . The layers of the OSI and TCP/IP models help to explain why these changes occur and the process that helps the data find its way from one node to the next. also have excellent explanations.com). networking models would be it. 9.3. such as Wikipedia (www. Keep in mind that peer layers communicate with each other. companies developed proprietary network technologies that naturally caused compatibility issues. Today you cover the Open System Interconnection (OSI) and TCP/IP layered models described in Modules 2. You might even have something to add to the Wikipedia explanations after your studies. so the OSI model was released in 1984. Many other online resources.2—When two nodes communicate. 2.5—Here is Yet Another OSI Model Chart (YAOMC).1—As you track the flow of information across a network. A solid understanding of these models prevents your network knowledge from resembling spineless.3. Module 2 2. A mnemonic such as Please Do Not Throw Sausage Pizzas Away might help you to remember each of the seven layers quickly for the exam.02_1587131749_DAY31. Look in the curriculum for related charts and graphics. Do not stop with the quick summaries provided today. 6.wikipedia. The benefits of using the OSI model to describe networks and networking devices are as follows: ■ Reduces complexity ■ Standardizes interfaces ■ Facilitates modular engineering ■ Ensures interpolable technology ■ Accelerates evolution of networks ■ Simplifies teaching and learning 2. Note that the protocol data unit (PDU) for each layer is in italics.3. they follow a protocol or an agreed upon set of rules to ensure the successful transmission of data. and 11 from CCNA 1 and the Cisco three-layer hierarchical model described in Module 5 from CCNA 3.3. It wouldn’t be a CCNA book without one.qxd 7/28/06 8:52 AM Page 3 Day 31 Describe Network Communications Using Layered Models If the CCNA had a skeleton.3. you will notice specific points where data changes on its route to a destination. 2. The networking models from CCNA 1 provide a framework for the concepts and configurations covered throughout the Cisco Networking Academy Program curriculum. CCNA 1.

Data is represented in a standard syntax and format such as ASCII. N/A 3 Network Packets are routed over the network and receive a path based on their IP address.3. Hub. and tear down for sessions between programs exchanging data.02_1587131749_DAY31. Table 31-2 The TCP/IP Model Versus the OSI Model TCP/IP Model OSI Model 4 Application 7 Application 6 Presentation 5 Session 3 Transport 4 Transport 2 Internet 3 Network 1 Network Access 2 Data link 1 Physical 2. the data remains data. The data link layer packages the packet into a frame and adds a source and destination MAC address. and flow control. and other programs that allow the user to enter data. The U. Table 31-2 matches the layers of the TCP/IP model with the OSI model. Department of Defense developed the model to define a network that could withstand nuclear war.qxd 4 7/28/06 8:52 AM Page 4 31 Days Before Your CCNA Exam Table 31-1 The Open System Interconnection Seven-Layer Model Layer Layer Name Number Function Devices 7 Application E-mail.7—The PDUs identified in the OSI model are encapsulated as they travel through the layers and from host to destination. Bridge. In the top three layers. error detection. N/A 6 Presentation Encryption and compression can occur.3. N/A 5 Session Set up. Finally.S. switch 1 Physical Bits physically pulse or wave their way over the network media representing 1s and 0s. FTP. . N/A 4 Transport Segments are transported with reliability. management. The network layer then packages the segments into packets and adds a source and destination IP address. wireless 2.6—The TCP/IP model achieves the same main goals as the OSI model. copper. repeater. When data enters the transport layer. it is packaged into segments. optical. Router 2 Data link Frames traverse the LAN with a MAC address as the identifier. the frame becomes a series of bits for transmission over the physical media.

The MAC sublayer controls access to the physical media. and successful transfer of a frame. Examples of these programs are as follows: ■ FTP ■ TFTP . 802. Unless otherwise noted.1—Three Layer 2 technologies that control how the physical media is accessed are Ethernet.02_1587131749_DAY31. Ethernet is nondeterministic and uses carrier sense multiple access collision detect (CSMA/CD) as the protocol for accessing the media.2—The application layer of the TCP/IP model includes programs and protocols that prepare the data to be encapsulated in the lower layers.3 Ethernet operates in the physical layer of the OSI model and in the MAC sublayer of the data link layer.1—Do not confuse the OSI and TCP/IP models despite the fact that some of the layers have the same name.1. most CCNA questions will reference the OSI model. Module 6 6.1. 9. The fields in a generic frame are as follows: ■ Start of Frame—This field identifies the beginning of a frame. These fields allow the receiving host to identify the beginning. (In this case. ■ The lower sublayer is the MAC sublayer. upper layers refers to Layers 3–7 in the OSI model and Layers 3 and 4 in the TCP/IP model.) ■ Frame Check Sequence—This field provides a number that represents the data in the frame and a way to check the frame and get the same number. Without frames. destination.5—Layer 2 frames are made up of fields. Module 9 9. and FDDI. the transmission would be just a big stream of ones and zeros. The LLC sublayer communicates with the upper layers of the OSI model. it identifies the Layer 3 protocol for the frame.1. As part of the MAC sublayer. The same layers in the different models have different functions.qxd 7/28/06 8:52 AM Page 5 Day 31 5 CCNA 1. This means that a node will first check to see if there is already a transmission and begin sending if the line is available. it defines the length of the frame. 6. Pay close attention to the layer name and model name in any layered model question. 6.3—The data link layer of the OSI reference model consists of two sublayers: ■ The upper sublayer is the Logical Link Control (LLC) sublayer. FDDI and Token Ring are deterministic in that they provide a way to take turns accessing the media. a collision will occur and both nodes will wait a random amount of time before trying again. these technologies can be divided into two groups: deterministic and nondeterministic. end. Cyclic redundancy check (CRC) is a common way to calculate the number and check for errors in the frame.1. ■ Data—Where the data resides that is processed by the upper layers.2. CCNA 1. Token Ring. ■ Length/Type—If this is a length field. ■ Address—This field contains the source and destination MAC address. if it is a type field. If two nodes transmit at the same time.

and session layers of the OSI model and that the TCP/IP network access layer includes the data link and physical layers of the OSI model. Examples of these protocols are as follows: ■ Ethernet ■ Fast Ethernet ■ Point-to-Point Protocol (PPP) ■ FDDI ■ ATM ■ Frame Relay 9. and acknowledgments. 11.qxd 6 7/28/06 8:52 AM Page 6 31 Days Before Your CCNA Exam ■ Simple Mail Transfer Protocol (SMTP) ■ Simple Network Management Protocol (SNMP) ■ Telnet ■ Domain Name System (DNS) 9.5—The TCP/IP network access layer. The trans- port layer achieves these goals through sliding windows. The TCP/IP internet layer also uses Address Resolution Protocol (ARP) to find a MAC address and Reverse Address Resolution Protocol (RARP) to find an IP address. provides the proto- cols to access the physical media and the standards for the media (wires.3—TCP and UDP operate as protocols of the TCP/IP transport layer. Module 11 11.3—In order to start passing segments at the transport layer.2—When two hosts establish a logical TCP connection at the transport layer. they agree on a reasonable flow of information. TCP.1—When you think about the transport layer. This layer includes the connectionless protocol IP and Internet Control Message Protocol (ICMP). whereas the TCP/IP model is the basis for development of the Internet. 9. consider flow control and reliability. 9. and is classified as a connection-oriented protocol. provides flow control.1. The OSI model appears more in academic and theoretical situations. also called the host-to-network layer.1.1.4—The TCP/IP Internet layer finds the path for packets over the network. The application initiating the connection and the operating system communicate . fiber.1.1.1. presentation.6—Pay close attention to the fact that the application layer of the TCP/IP model includes the application. two hosts must set up and maintain a session. UDP is a connectionless protocol that sends the data without verifying a successful transfer. segment sequence numbers. Both TCP and UDP segment data from the TCP/IP application layer and send the segments to the destination host. 11. ensures reliable transfer with acknowledgments and sequencing.02_1587131749_DAY31. and radio frequency). This flow control allows the receiving host to process the information in time to receive new segments from the sending host. Know both models.1. however. CCNA 1.

If a sending host fires segments 1.1. and 6. The fields of a TCP segment are as follows: ■ Source port ■ Destination port .6—How does the sending host know to retransmit a segment? As mentioned previously. the sending host’s need to retransmit relies on the numbers sent with acknowledgments. retransmission occurs in the negotiation of a window size.7—FTP.1.qxd 7/28/06 8:52 AM Page 7 Day 31 7 with the receiving host’s application and operating system to set up and synchronize a session. Figure 31-1 TCP Sliding Window Sender Receiver Send 1 Send 2 Send 3 Receive 1 Receive 2 Receive 3 Send ACK 4 Receive ACK 4 Send 4 Send 5 Send 6 Receive 4 Receive 5 Receive 6 Send ACK 7 Receive ACK 7 Window Size = 3 11. 11. as shown in Figure 31-1. SMTP. Send a SYN.1. These sliding windows control flow between the two hosts.5—TCP can play with these ACKs to define how much can be sent using sliding windows. reliable transfer that TCP provides. and you are connected using the TCP protocol. 5. To further explain the process.1. TCP avoids congestion at the transport layer by allowing the receiving host to send ready and not ready indicators to the sending host. This three-way handshake defines the sequencing for TCP communication.6 in the CCNA 1 curriculum. and Telnet use the transport layer TCP protocol. If at some point during this transfer the receiving host does not acknowledge the transfer. A host initially sends a segment with a window size of 1.4—Applications that use the connection-oriented protocol TCP at the transport layer must first set up a session.) If you need help. the sending host would have to retransmit segment 3. The sending host shoots back two segments and the receiving host acknowledges and asks for a window size of 3. Remember that both hosts must send an initial sequence number and receive an acknowledgment for communication to proceed. it knows to send segments 4. receive an ACK. 11. and 3 over to the receiving host and receives an ACK 4. All of these protocols benefit from the connection-oriented.1. visit module 11.02_1587131749_DAY31. The receiving host could respond with an acknowledgment and identify that it would like a window size of 2. If the receiving host were to return only an ACK 3. (You can use the “Your Notes” section that appears after today’s summary. 2. HTTP. 11. the sending host tries again with a smaller window size. send back an ACK +1. Try illustrating this process.

The destination host must connect on a standard port number while the source host dynamically assigns a number above 1023 for the source port number. UDP streams its segments at the receiving host and leaves the error checking to the upper-layer protocols. Notice in the following UDP fields that there are no acknowledgement.1.9—If someone connects to your desktop on port 27015. and window fields: ■ Source port ■ Destination port ■ Length ■ Checksum ■ Data 11. Memorize the common registered TCP and UDP port numbers for the protocols included in Table 31-3.8—TFTP. and DNS use the connectionless transport layer protocol UDP.qxd 8 7/28/06 8:52 AM Page 8 31 Days Before Your CCNA Exam ■ Sequence number ■ Acknowledgment number ■ Header length (HLEN) ■ Reserved ■ Code bits ■ Window ■ Checksum ■ Urgent pointer ■ Option ■ Data 11. This port is not one of the well-known port numbers assigned by the Internet Assigned Numbers Authority (IANA) because it provides standard port numbers below 1024 for protocols such as FTP (port 21 TCP) and HTTP (port 80 TCP). you are likely hosting a video game.1. sequence. SNMP.02_1587131749_DAY31. DHCP. Table 31-3 Transport Layer Ports Application Layer Protocol Transport Layer Port/Protocol http Port 80 TCP FTP Port 21 TCP Telnet Port 23 TCP SMTP Port 25 TCP DNS Port 53 UDP and TCP TFTP Port 69 UDP SNMP Port 161 UDP RIP Port 520 UDP .

The threelayer hierarchical model has three layers. The core layer serves as the backbone reserved for high-speed transmission. If you have the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. now is a good time to review pages 13–34. which provide an outline for the types of devices and connectivity necessary in a large network. Each domain name has an extension such as . Only four layers comprise the TCP/IP model. to packets. In the “Your Notes” section that follows. and then to bits. . SNMP SNMP allows an administrator to observe activity and troubleshoot problems on a network. CCNA 3. Module 5 5. distribution.1—Networking engineers use a three-layer hierarchical model to describe and design networks. Summary The OSI model and its seven layers cover each aspect of networking as data changes to segments.2. Second Edition (ISBN: 1587200791). HTTP HTTP uses TCP and allows a user to navigate web sites on the Internet using a browser. SMTP SMTP uses TCP at OSI Layer 4 to send e-mail.02_1587131749_DAY31. A network management system can collect information provided by network devices. and access layers. Table 31-4 Application Layer Protocols Protocol Description DNS The DNS represents an IP address with a domain name. This model consists of the core. to frames. The distribution layer divides the core layer from the access layer and provides policy-based connectivity.2.7—Each of the application layer protocols in Table 31-4 provides a key function for Internet use.qxd 7/28/06 8:52 AM Page 9 Day 31 9 11. It is possible to transfer Cisco IOS images using TFTP.com that helps to identify the purpose of the site. The access layer connects users and remote sites to the network. published by Cisco Press. it would be wise to diagram each of these layers and their characteristics from memory.2. FTP and TFTP FTP allows connection-oriented TCP-based file transfer between a client and a server.1–11. Telnet Telnet provides a command-line interface to a remote host. exam #640-801). TFTP uses the connectionless UDP protocol to transfer files without the feature set of FTP.

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CCNA 3.2. switches start out by sending BPDUs across the network that allow each switch to identify the root bridge and build a logical tree by turning off nondesignated ports and maintaining a single link with designated ports. The logical tree starts at the root bridge. Each switch assumes that it is the root bridge and initially sends out its BID as the root ID.3—BPDUs spread across the network. To avoid loops. STP uses the spanning tree algorithm to turn off redundant connections until they are needed.1d standard and identifies the shortest paths in a switched network to build a loop-free topology. switches that are closest to the LAN become designated switches to forward traffic from that LAN.2. but if a switch does not know the destination MAC address of a frame. 7. A switch that does not have the lowest BID will replace its ID as the root bridge with the lowest BID that it receives from other switches. The switch with the lowest BID becomes the root bridge. Each nonroot bridge will have one root port. and the network is converged.2—STP is defined by the IEEE 802. The network should now have only one root bridge per network and one designated port per segment. a switch has no way of recognizing and discarding a frame that it has already received.1—Switches filter by MAC address.03_1587131749_DAY30.6.1. but if you start to add backup connections to a switched network it is imperative to also run the Spanning Tree Protocol (STP). redundantly connected switches must create a logical tree over which to send frames using the spanning tree algorithm. .4—To determine the root bridge. Module 8 from CCNA 1 and Module 7 from CCNA 3 describe STP and its operation. Designated ports and root ports can forward data traffic. 7. A BID contains the bridge priority number (32768 by default) and the switch MAC address. If there are multiple LAN segments. As mentioned previously in the section “CCNA 1. A switch can forward a frame forever.1. switches also send a bridge ID (BID) with BPDUs. a network administrator needs to set the bridge priority number. Switches running STP send bridge protocol data units (BPDUs) out each port to identify and block redundant paths. To ensure that a certain switch becomes the root bridge. All switch ports can transition from blocking to learning to listening and then to forwarding during this process. Module 8” under 8. switches block nondesignated ports.6—Redundantly connected switches provide a valuable backup connection. CCNA 1. the logical tree is in place.qxd 7/28/06 8:52 AM Page 11 Day 30 Describe the Spanning Tree Process Switches can filter frames by MAC address and can speed up a network. At Layer 2.2. The designated port is the only port to forward STP traffic onto the segment under normal converged conditions. Module 7 7.2. it broadcasts (floods) that frame out all ports except the receiving port. Module 8 8. 7. but it is important that these backup connections do not cause loops.

Dive in and make your best attempt with the understanding that it is your first attempt. spanning tree has successfully set up a logical tree and the network has converged.1w Rapid Spanning Tree Protocol (RSTP) does it faster. In your notes. and processes BPDUs. try drawing three diagrams—one that explains how a switching loop could occur.7—IEEE 802.2.5—Table 30-1 defines the states that a switch port can cycle through when connected to a network. switches use STP or RSTP. Second Edition (ISBN: 1587200791). in the online curriculum has some great examples if you need help. Listening The port checks for multiple paths to the root bridge and blocks all ports except the port with the lowest cost path to the root bridge. 7. The small amount of material covered today also gives you an opportunity to take your first timed Networking Academy online CCNA practice exam. but IEEE 802. . published by Cisco Press. exam #640-801).03_1587131749_DAY30. A change in the physical topology of a network causes spanning tree recalculation to occur in order to once again achieve convergence. Module 7.1d STP prevents switching loops. If you have the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. one that explains identification of the root bridge (showing BIDs). Forwarding The port learns MAC addresses.2. 7.6—If all switch ports on a network are only in blocking or forwarding mode. forwards data. CCNA 3. Point-to-point and edge-type links in RSTP can cycle directly from blocking (renamed discarding) to forwarding. Table 30-1 Spanning-Tree Port States Port State Description Blocking The port looks only at BPDUs. Summary To achieve convergence and a logical tree with no loops. Learning The port learns MAC addresses but does not forward data.qxd 12 7/28/06 8:52 AM Page 12 31 Days Before Your CCNA Exam 7.2. RSTP can converge in 15 seconds. Remember that a switch port can also be administratively disabled. and one that depicts a converged network with each port labeled. you might thumb through pages 301–329. while STP takes up to 50 seconds.

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peripheral devices. Module 1 from CCNA 2.04_1587131749_DAY29. and Modules 4 and 5 from CCNA 3 provide the information needed to properly characterize a LAN environment. network interface cards. CCNA 1.1.6—Computers. You most often use Ethernet. Module 6 6. The two most common logical topologies are token-passing or broadcast. These rules are defined as protocols. and network devices make up the main parts of a LAN. Token Ring.1.1. or FDDI in LAN technologies. The IEEE assigned those first six hex numbers to Intel (the company that made the network card).qxd 7/28/06 8:52 AM Page 15 Day 29 Compare and Contrast Key Characteristics of LAN Environments From casinos in Las Vegas to basements filled with mouse-clicking gamers. These terms include the following: ■ Bus—All devices connected to one single arterial cable ■ Ring—Each host connected to two other hosts forming a ring ■ Star—All hosts connected to a hub or switch ■ Extended Star—Hosts connected to a hub or switch that is in turn connected to a hub or switch ■ Hierarchical—A pyramid of extended star networks all connecting to a main proxy that handles traffic at the top of the pyramid ■ Mesh—All hosts directly connected to all other hosts Logical topologies determine how the hosts communicate across the medium. and how to handle errors. called the Organizational Unique Identifier (OUI). Network protocols control the type of connection. How you characterize and define the physical and logical topologies of these LANs is the key to configuring and troubleshooting them.1. networking media. A MAC address can also be called a burned-in address (BIA). Each frame that a . 2. CCNA 1. how data is transferred. Module 2 2.4—00-B0-D0-06-00-A3 is the 48-bit MAC address of the host that I am using to write this section. Intel gets to assign the last six hex numbers.4—The terms to describe the physical topology of a network help you to explain how all the devices are connected. 2.5—Networks need a set of rules to determine how they communicate. Modules 2 and 6 from CCNA 1. you encounter LANs.

7—The fields of an Ethernet frame are as follows: ■ An Ethernet frame begins with a preamble made up of alternating 1s and 0s. Initially. Module 1 1.1. can filter each port based on the Layer 2 MAC address and provide a separate collision domain for each connected device. Networks could now be divided into two separate collision domains. If you build a LAN today. for example.1—Ethernet 802. so the potential for a collision existed on the entire network. Layer 2 bridges were introduced and did not just retime and regenerate the signals like a hub. but also listed the length/type field as just type.6—Ethernet frames did not always have a length field. so a Layer 3 router functions as the gateway that filters all LAN traffic and only forwards information destined for other connected LANs.3 LANs started as simple networks connected with a hub or concentrator and evolved into sophisticated topologies operating on many layers of the OSI model. 0x0800 hex is IP. became common in networks as a way to retime and amplify signals to devices now connected in a star topology. it represents the type of protocol. LANs connected using thick Ethernet and thin Ethernet using a bus topology.04_1587131749_DAY29. or multiport bridge. This switch.3 Ethernet. Hubs. or multiport repeaters. CCNA 3. The original Digital Intel and Xerox (DIX) version of Ethernet (Ethernet II) not only combined the preamble and start of frame delimiter. TCP/IP today uses a length/type field to identify upper-layer protocols in IEEE 802.1. 6. Switches and bridges do not filter broadcasts. . Routers communicate with each other to build routing tables allowing them to select the best path for a data packet between LANs.3—A LAN connects to other LANs and the Internet through a router. CCNA 2. If the Length/Type field is greater than or equal to 0x600 hex. ■ The Destination and Source Address fields are next. ■ The Length/Type field follows. ■ The Data field is followed by the Frame Check Sequence (FCS) field. If the Length/Type field is less than 0x600 hex.1. This segments the LAN from other LANs and reduces overall traffic. ■ The Data field contains information to be handled at the next layer. Bridges were able to look at the MAC address and decide whether or not to forward a frame.1. 6. A router will only forward data outside of a LAN if it is destined for another network.qxd 16 7/28/06 8:52 AM Page 16 31 Days Before Your CCNA Exam host sends over the LAN includes a destination MAC address. ■ The Start of Frame delimiter identifies the end of the preamble with the byte 10101011. All hosts on that LAN drop the frame unless the destination MAC address in the frame matches the MAC address of the host. All signals traveled over the hub network to all devices. it represents the length of the data in the next field. The router acts as the gateway for LAN devices and operates at Layer 3 of the OSI model. you will likely connect devices with a switch. Module 4 4.

Switches divide collision domains and only pass frames over the wire to hosts with the proper destination MAC address. Switches do not divide broadcast domains. consider how many hosts populate each collision and broadcast domain.6—Network latency slows connectivity and is an especially sour term for network gamers.1. Layer 3 devices can increase latency because they take more time than a Layer 2 device to process network data. The time it takes a network interface card (NIC) to receive or place a signal on a wire and the time it takes that signal to travel over the network contributes to latency. The collisions mentioned in this section under 4.1.8—Remember that devices can send out Layer 2 broadcasts to contact all hosts with a desti- nation MAC address of FF-FF-FF-FF-FF-FF.04_1587131749_DAY29.2. “Design a Simple LAN Using Cisco Technology. You will revisit all of Module 5 from CCNA 3 on Day 23. This type of connection allows each of the two hosts to both transmit and receive at the same time.3.3.qxd 7/28/06 8:52 AM Page 17 Day 29 17 4. Initially. switches can use MAC addresses to create direct virtual connections between two hosts on a network.1. and switches improve network functionality because they protect hosts from unnecessary traffic. this is defined as carrier sense multiple access collision detect (CSMA/CD). These frames are still broadcast to all hosts by switches. 4.1. each port on a switch is its own collision domain. This full-duplex communication uses all the bandwidth in both directions. Use switches to segment collision domains and routers to filter broadcasts.2—When you design a LAN. 4.” . In cut-through mode. 4.1 occur when two devices attempt to transmit or receive at the same time. the higher the potential for a collision. Switches can operate in cut-through or store-and-forward modes.1. Excessive collisions can congest a network.2—In addition to cut-through or store-and-forward modes. The more devices you connect to a hub on a half-duplex network. allowing for a 20 Mbps connection on a 10 Mbps network. the switch operates in cut-through until there are a certain number of errors that cause it to switch to store-and-forward. 4. 4. a switch either sends the frame as soon as it knows the destination MAC address (fast-forward) or reads the first 64 bytes and then sends the frame (fragment-free).4—Shared Ethernet networks that operate in half-duplex can allow only one host to transmit or receive at a time. This mode is a combination of cut-though and store-and-forward.7—The host-to-host virtual circuit that a switch creates can be referred to as microsegmenta- tion. It would be difficult to sell IP phones to a school connected with all hubs. CCNA 3. 4. bridges.1. the device that notices the collision sends a jam signal.1.3. On an Ethernet network. Store-and-forward mode results in the switch receiving the entire frame before forwarding the information. and both devices wait a random amount of time (based on a backoff algorithm) before attempting to use the network again. When this happens. 4. the Internet would be pretty darn slow. Routers filter broadcasts and forward only packets that are destined for other networks to other ports.3. Because switches can microsegment networks into virtual circuits based on the MAC address filtering.9—As mentioned previously in this section under 4.5—Routers. switches can also operate in adap- tive cut-through mode. Without routers to filter these broadcasts. Module 5 5.10—The latency caused by a switch relates directly to how it processes a frame. for example.

How you use network devices and physical design to organize a LAN will decide the speed and efficiency of your network.qxd 18 7/28/06 8:52 AM Page 18 31 Days Before Your CCNA Exam Summary LANs provide the local connectivity that supports business as well as important entertainment and therapeutic applications. Your Notes . In your notes you might sketch each of the physical and logical topologies that this chapter mentions.04_1587131749_DAY29. exam #640-801). Second Edition (ISBN: 1587200791). It would also help to quiz yourself on pages 36–60 of the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. if you have one sitting near you.

2. IP and Internetwork Packet Exchange (IPX) are examples of routed protocols. 6. AS numbers keep networks in manageable groups that allow routers to converge more quickly. Enhanced Interior Gateway Routing Protocol (EIGRP).2. CCNA 2. An AS number allows a network to represent itself as one unit. and 3 from CCNA 3 shed light on the routing protocols that are important to passing the CCNA exam. 6. Examples of routing protocols include Routing Information Protocol (RIP). The administrative distance for a static route is 1 by default. If the network changes.1—Routers use routing protocols to communicate with each other about networks and network locations.05_1587131749_DAY28. and Open Shortest Path First (OSPF).1.2. so a 1 can only be bumped by a directly connected route with an administrative distance of 0. Routing protocols can even have elections…kind of. In the routing table. 6.2.2. routers must recalculate the routing tables using a dynamic routing protocol.2—Routing tables would be huge if there were no way to divide large networks into smaller groups of networks. You must not confuse a routing protocol with a routed protocol. the router adds that route to the routing table. Autonomous system (AS) numbers do just that with a 16-bit number assigned by the American Registry of Internet Numbers (ARIN). 6.2—Once an administrator has configured a static route. How do routers know the best path for a packet? Either you tell them with a manually configured static route or the router uses a dynamic routing protocol to find out about the network topology and build its own routing table. Interior Gateway Routing Protocol (IGRP).4–6. Distance vector routing protocols look at how far away a route is and the direction (vector) to reach it.1—Routers choose a path over the network for a packet based on its destination IP address.3—Routers achieve convergence when all routers share a common view of the network via their routing table.1.qxd 7/28/06 8:53 AM Page 19 Day 28 Evaluate the Characteristics of Routing Protocols Routing protocols are the legislators of the Internet.2. .6—Routers can communicate about routes dynamically using one of the two classes of routing protocols in Table 28-1. Module 6 6. Link-state routing protocols build a topology of the entire network. Routed protocols provide the information in a packet that allows the router to properly forward said packet. Modules 6 and 7 from CCNA 2 and Modules 1. They constantly discuss and define the rules for what data goes where and what paths the data must take. You can configure a static route as a backup route if you give it an administrative distance that is higher than a dynamic route in the routing table. the route with the lowest administrative distance wins. 6.

Routers see only neighboring routers.0. distance vector Used to route between autonomous systems 6. load. Routers flood LSAs only when there is a topology change. 6. it first looks at the destination address and compares it to its routing table. If two networks. and reliability OSPF Link-state Nonproprietary protocol that updates only when there is a change in topology EIGRP Hybrid Cisco proprietary protocol that uses both link-state and distance vector features and multicasts updates on 224. Table 28-2 Routing Protocols Protocol Name Type Description RIP Distance vector Broadcasts updates every 30 seconds and uses hop count as the metric with a maximum of 16 IGRP Distance vector Cisco proprietary protocol that broadcasts updates every 90 seconds and uses a composite metric of bandwidth.0.3. The router uses the routing table to determine the best path for the packet and forwards it out the appropriate port. 6. for example a company and an ISP. the entire routing table to neighbors. Routers use a metric to determine the best path for a route and build a routing table. have different administrators and separate interior routing protocols.3.3.10 BGP Exterior. Routers use the Shortest Path First (SPF) algorithm and LSAs to build a shortest path tree as well as a routing table. delay. Routers use the LSAs to build a full topology of the network.3—Each of the routing protocols described in Table 28-2 function at the Internet layer of the TCP/IP model.4—Table 28-2 shows how autonomous systems are able to communicate. Border Gateway Protocol (BGP) is provided as an example of an exterior gateway protocol.qxd 20 7/28/06 8:53 AM Page 20 31 Days Before Your CCNA Exam Table 28-1 Distance Vector and Link-State Protocols Distance Vector Link-State Routers send periodic updates of Routers send link-state advertisements (LSAs) to update other routers. To develop a full loop-free topological database requires more memory than a distance vector protocol requires of a router. they can use BGP on their gateway routers to exchange information about directly reachable networks.05_1587131749_DAY28. .1—When a router receives a packet on a port.

RIP uses only hop count as a metric to consider a path. This process is aptly named route poisoning. Routing updates occur every 30 seconds with RIP.3. 7. 7. Split horizon prevents this type of loop when it states that routerA cannot receive an update that concerns routes that routerA originally advertised.3—The key to finding the proper path.4–7. Routing updates occur every 90 seconds with IGRP. Distance vector routing protocols monitor the distance a packet travels as it passes over the network to avoid this type of loop. and for that matter many tombstones as well (bad joke). IGRP focuses on speed as the main reason to use a particular route. RIP tracks a packet with hop count and deems a network unreachable if it appears over 15 hops away. a router ignores its regular schedule and shoots out the poisoned route information as soon as it notices that a network is down. A router can also prevent loops by poisoning a route for a network that has gone down.1.7—If routerA updates two connected routers that network1 is down but then accepts a later update from one of those same routers that network1 is reachable. Typically. The default metrics used by IGRP are bandwidth and delay. A router on the network may not receive an update that a link is down and proceed to advertise that it can get to the network. it just means that all routers know about the change.1 and 7.1—Linksys home router supports RIP. With route poisoning and triggered updates. . This scenario is possible because one of the connected routers may be getting old information from another part of the network originally sent out by routerA. the packets destined for the network could continue to pass around the network continuously. Components of a routing metric could be any of the following: ■ Internetwork delay ■ Bandwidth ■ Load ■ Reliability ■ Hop count Routers using a distance vector routing protocol exchange routing tables with neighbors to learn the metric and best path. This could cause routing issues if a network goes down and a router has to wait 30 seconds to send its next update.1.2—IGRP is also a distance vector routing protocol.3. it adds a hop to the route to represent itself in the path to the destination. The maximum hop count of 16 ends the routing loop. Module 7 7. as mentioned previously. If these routers do not exchange routing tables quickly enough in a changing network. 7. but IGRP can also be configured to use load and reliability. RIP will identify a network as unreachable if it has a hop count over 15.1. This problem is avoided with triggered updates.05_1587131749_DAY28. you could have a loop. Routers implement a holddown timer that causes them to wait a set amount of time before actually removing a route from the routing table. This does not mean that routers immediately remove the route from the routing table.qxd 7/28/06 8:53 AM Page 21 Day 28 21 CCNA 2. Each time a router running RIP receives an update.2. RIP is a distance vector routing protocol that implements split horizon and holddown timers. distance vector routing protocols update only on a set interval.1–7. lies in the routing met- ric. they can form a loop.1. A router can accomplish this by sending out the maximum hop count for a route as soon as it sees that the network is unreachable. If this router is able to update other routers with this information.

3—RIP. Routers can learn about other networks through static and dynamic routes.255.1. “Design an IP Addressing Scheme to Meet Design Requirements. whereas RIP version 2 more efficiently multicasts on the Class D address 204. and exterior routes. Interior routes are between networks that are connected to a router and have been divided into subnets.1–2. OSPF proves itself a good choice for a large network because unlike RIP it allows more than 15 maximum hops and large networks can be divided into areas. This is a partial truth. but LSAs remain the key way that link-state protocols discover information across the entire network. as mentioned previously in “CCNA 2. use the Dijkstra algorithm to determine the shortest path for each network.2. 2. When a network changes. 2. CCNA 3.2. This means that RIP version 2 supports variable-length subnet masks (VLSMs) and classless interdomain routing (CIDR). Module 1 1. CCNA 3. You will cover IP addressing and VLSM on Day 27. a router will flood LSAs on a specific multicast address across the specified network area.7—All routers on the Internet cannot contain a route for every network that exists.2. and poison reverse. Module 7. For this reason.6—Table 28-1 implies that link-state routing protocols send updates only when the net- work changes.” and Day 22.1. Flooding LSAs across a network can affect overall bandwidth on a network and cause each router to recalculate a full topological database. split horizon. Module 2 2.05_1587131749_DAY28. and use the tree to build the routing table. system. but for traffic destined outside of the immediate network an administrator can add a default route. A default route provides a destination for a router to forward all packets for which it does not have an entry in its routing table. Link-state protocols actually send little hellos periodically to obtain information about neighboring routers.255. build the shortest path tree. 1. These areas communicate with a backbone area to reduce routing protocol traffic and routing table size.4—IGRP can advertise interior. Sorry.9. IGRP increases its stability as a routing protocol by using holddown timers. In addition to the topological database.0.3. System routes are between networks inside of an autonomous system.2.2–2.255.3.qxd 22 7/28/06 8:53 AM Page 22 31 Days Before Your CCNA Exam 7. “Evaluate the TCP/IP Communication Process and Its Associated Protocols. a network using a link-state protocol must be broken up into small enough areas to maintain network efficiency and use routers with sufficient memory and processing power.” Another difference between RIP versions 1 and 2 is in how each protocol sends updates. RIP version 1 broadcasts updates on the address 255.1–1.2. each .4—OSPF-enabled routers are true to their link-state definition in that they maintain a full loop-free topological database of the network. Exterior routes define access to networks outside of an autonomous system.1—OSPF is a nonproprietary link-state protocol that allows you to control the flow of updates with areas.0. RIP version 2 adds authentication and the ability to send a subnet mask with routing updates.2. These LSAs allow the router to create a topological database of the network.3 and 7.” is a distance vector routing protocol that uses hop count as a metric and implements both holddown timers and split horizon.

and rapid convergence through LSAs are key features of OSPF. If the connection is broadcast or point-to-point. 2. or nonbroadcast multiaccess networks such as Frame Relay elect a single router called the DR to handle updates. A router running only IGRP will see EIGRP routes as IGRP routes. 2. all routers would technically be connected on the fiber ring to each other. Module 3 3.2.05_1587131749_DAY28. Routers that are connected on broadcast multiaccess networks like fiber. Each router then will have two adjacencies: one for each directly connected neighbor. a loop-free SPF tree. OSPF-enabled routers also elect a designated router (DR) and backup designated router (BDR) as central points for routing updates.5. whereas IGRP does not. Periodic hello packets can alert routers to a change in the topology that would restart the process. To avoid a single point of failure. . The contents of the hello packet include the following: ■ Version ■ Type ■ Packet length ■ Router ID ■ Area ID ■ Checksum ■ Authentication type ■ Authentication data 2. If they are on a multiaccess link. VLSM support.2. Ethernet.0.qxd 7/28/06 8:53 AM Page 23 Day 28 23 OSPF-enabled router maintains a unique adjacency database that tracks only neighboring routers. Once adjacencies exist between neighbors. a DR and BDR election occurs. the routers forward LSAs and add information to their topological databases.1—EIGRP and IGRP routing protocols function seamlessly together despite the fact that EIGRP offers multiprotocol support and functions as a hybrid routing protocol. Once the topological databases are complete.6—Those little OSPF hello packets typical to link-state protocols go out over the multicast address 224. Routers first determine if they are on a point-to-point link or multiaccess link. OSPF avoids a network of neverending neighbors with an election.2. This means that each router would be a neighbor to every other router.0.7—The OSPF process starts with hello packets to find neighboring routers and develop adja- cencies. they also elect a BDR. the hellos default to 10 seconds. the routers use the SPF algorithm to create the SPF tree and then a routing table. EIGRP also supports VLSM.5—The OSPF adjacency databases are just great if you happen to be working with a Cisco Academy router pod with four routers each connected with point-to-point connections. CCNA 3. a bandwidth-based metric. the packets default to 30 seconds. and if the connection is nonbroadcast multiaccess (NBMA). If you were to run OSPF on a fiber network.1.

are kept only in the topology table. EIGRP also develops neighboring relationships with other routers.0. In the topology table. 3. EIGRP can also tag routes as internal or external. EIGRP defines the following fields: ■ Feasible Distance (FD)—The lowest cost to each destination ■ Route Source—The router identification number for externally learned routes ■ Reported Distance (RD)—A neighboring router’s reported distance to a destination ■ Interface Information—Which interface to use to reach a destination ■ Route Status—The status of a route. EIGRP has a modular design that uses protocol-dependant modules (PDMs) to support other routing protocols. sends out partial updates and hello packets.05_1587131749_DAY28. EIGRP also maintains a topology table that contains routes learned from all configured network protocols.2—As a hybrid multiprotocol routing protocol. IPX.1. ■ Independence from routed protocols—EIGRP supports IP. or feasible successor routes. If a network goes down and there is no feasible successor. sends query packets out to neighbors. and external routes come from other routing protocols and outside the EIGRP AS. the router sets the route to active.qxd 24 7/28/06 8:53 AM Page 24 31 Days Before Your CCNA Exam 3.10 to communicate with neighbors ■ Acknowledgment—Hello packets without data sent to acknowledge receipt of a message . but these packets go only to routers that need the information. EIGRP collects multiple databases of network information to build a routing table. and begins to rebuild the topology.1. or the successor route.5—EIGRP uses five different types of packets to communicate with other routers: ■ Hello—Sent on 224.1.0. In the topology table.1. ■ Efficient use of bandwidth—EIGRP. EIGRP uses a neighboring table in the same way that OSPF uses an adjacency database to maintain information on adjacent routers. EIGRP.3 and 3. EIGRP uses functions from both link-state and distance vector protocols. ■ Multiple network layer support—Rather than rely on TCP/IP to send and receive updates. where ready-to-use routes are identified as passive and routes that are being recalculated are identified as active The neighbor and topology table allows EIGRP to use DUAL to identify the best route. Like OSPF. Internal routes come from inside the EIGRP AS. and enter it into the routing table. Backup routes.4—Advanced features of EIGRP that set it apart from other distance vector routing protocols include: ■ Rapid convergence—EIGRP uses the DUAL finite-state machine (FSM) to develop a full loop-free topology of the network allowing all routers to converge at the same time. and AppleTalk. however. ■ Support for VLSM and CIDR—EIGRP sends the subnet mask information allowing the network to be divided beyond default subnet masks. 3. uses a distance vector diffusing update algorithm (DUAL) to recalculate a topology. like OSPF. EIGRP uses the reliable transport protocol as its own proprietary means of sending updates. so changes to reflect revisions in the other protocols have to be made only to the PDM and not EIGRP.

you might flip through pages 388–450 and focus on the details of routing protocols.1. If there is no feasible successor. you know how it is possible for the Internet to function and send so much data to so many hosts.05_1587131749_DAY28.1. exam #640-801). EIGRP-enabled routers build a topology table that contains and uses the DUAL algorithm to select the successor routes that will populate the routing table. If a link goes down. Summary Make sure you know the difference between a distance vector routing protocol and a link-state protocol. the DUAL algorithm selects a feasible successor from the topology table and promotes it to the successor route. If you happen to see a copy of CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. You can focus on the commands on a later day.qxd 7/28/06 8:53 AM Page 25 Day 28 ■ Update—Used to update new neighbors so that they can in turn update their topology ■ Query—Used to gather information from one or many neighbors ■ Reply—Sent as response to a query packet 25 3. Second Edition nearby. EIGRP recalculates the topology table.6—As described in CCNA 3 Module 3.2. If you understand routing protocols. This process and the DUAL algorithm enable EIGRP to achieve rapid convergence. It is not uncommon for the CCNA exam to test your understanding of routed vs. routing protocols as well. .

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06_1587131749_DAY27.9. 10. and 11 from CCNA 1 and Modules 8 and 10 from CCNA 2 outline the TCP/IP process and the associated protocols. and even the recording industry have taken great interest in the TCP/IP communication process. 1.2. Boolean logic compares two numbers and provides a result based on the AND operator. Expect more on IP addressing on Day 22.6—Understanding binary is important in order to understand IP addressing.2. TCP/IP is the postal system that allows devices on the Internet to differentiate between one host and the next.2.” CCNA 1. “Design an IP Addressing Scheme to Meet Design Requirements. Look at how the two columns relate and see if you can complete the last two rows. 2. Modules 1. “Describe Network Communications Using Layered Models. Sometimes you will need to convert an IP address to its binary format when developing an IP addressing scheme for a network.” as well as learn new information. Table 27-1 shows the powers of 2 for each bit from left to right and the decimal equivalent in the other section. Table 27-1 Binary to Decimal Conversion Bits and Powers of 2 Decimal Equivalent 1 128 1 64 1 32 1 16 1 8 1 4 1 2 1 1 128+64+32+16+8+4+2+1 = 255 1 128 0 64 0 32 1 16 0 8 0 4 1 2 1 1 128+16+2+1 = 147 0 128 1 64 1 32 0 16 0 8 0 4 1 2 0 1 128 64 32 16 8 4 2 1 1 128+2+1 = 131 1. . video game developers. Decimal to binary conversion requires that you determine what bits contain a 1 and what bits contain a 0. When a router receives an IP address in a packet.qxd 7/28/06 8:53 AM Page 27 Day 27 Evaluate the TCP/IP Communication Process and Its Associated Protocols Network administrators. Table 27-2 shows the rules for the AND operator and gives an example of applying an AND operation to an IP address and subnet mask to determine the network address.7.10—A 32-bit IP address is made up of four sets of numbers. Module 1 1.2. and 1. 9. the router uses Boolean logic to compare the IP address to the subnet mask and determine the network address. or octets. Each octet contains an 8-bit binary number like those shown in Table 27-1.2.5 and 1. You will quickly review some concepts from Day 31.

SMTP. Module 2 2.1–9.10101000.00000001. however. TFTP.168.11111111. and DNS. 9. IP operates at the Internet layer and includes Ethernet.00000111 1 AND 0 = 0 Subnet mask 11111111.06_1587131749_DAY27.0 CCNA 1. but the OSI model is often used in academic and theoretical situations because it further divides the networking process. PPP.1. ATM. The application layer includes protocols such as FTP. and the Corresponding PDU TCP/IP Model OSI Model PDU 4 (application) Application (Layer 7) Data Presentation (Layer 6) Session (Layer 5) 3 (transport) Transport (Layer 4) Segments 2 (internet) Network (Layer 3) Packets 1 (network access) Data Link (Layer 2) Frames Physical (Layer 1) Bits CCNA 1. and FDDI.7–9. as well as IEEE specifications for physical media.3.6 and 2.1. On multiple LANs divided by Layer 3 routers. TCP and UDP operate at the transport layer.1. as well as the protocol data units (PDUs) used in each layer.6—As covered on Day 31. This allows a router to keep a . Module 9 9. routers use the Internet Protocol (IP).255.10101000. the TCP/IP model is made up of four layers.00000001.00000000 1 AND 1 = 1 Result Mask 255. IP addressing goes beyond unique identification to provide grouping by networks.7 0 AND 1 = 0 IP address 11000000. To identify networks and get information to hosts.qxd 28 7/28/06 8:53 AM Page 28 31 Days Before Your CCNA Exam Table 27-2 Using the AND Operator to Determine a Network Address AND operator IP Address and Subnet Mask to Network Address 0 AND 0 = 0 IP address 192.168.00000000 Network address 192. MAC addresses work wonders on a LAN at Layer 2 to identify computers for switching.1.1. Table 27-3 The TCP/IP Model Versus the OSI Model.11111111. Frame Relay.0 11000000.255.2. The TCP/IP model is the basis of the Internet.3.3— The Internet is made up of thousands of internetworks connected by routers through various types of physical media.7—Table 27-3 summarizes the information presented from Day 31 about the lay- ers of the TCP/IP model as compared to the OSI model.

Despite the fact that binary looks cooler.168.N. The broadcast address.0 192. Table 27-5 provides as much information as will fit about address classes. 9. Table 27-5 Class A. Table 27-4 One Octet of an IP Address Bits and Powers of 2 1 128 1 64 1 32 1 16 Decimal Equivalent 1 8 1 4 1 2 1 1 128+64+32+16+8+4+2+1 = 255 So how does an IP address display information about the specific host and the network? Part of an IP address represents the host.255 192.2. The broadcast address for a network is where the host portion is made up entirely of binary 1s. The first few binary digits in an IP address define the default address class.4—IP addressing is by default broken up into a set of classes that define the network and host portions.168. dotted decimal is easier to read.H.0 192. This is like putting the name of your city on an envelope to represent where your house is located. The network address for a specific network is where the host portion is made up entirely of binary 0s.qxd 7/28/06 8:53 AM Page 29 Day 27 29 shorter table of network locations and not individual IP addresses.H. converting binary IP addresses to decimal and back is all about the powers of two.168. Table 27-6 Network and Broadcast Address Example Network Default Class C Binary Host All 0s Network Address Binary Host All 1s Broadcast Address Useable Hosts 192.H 65. cannot be assigned to a specific host.H Multicast 28 Class E 1111 240–255 RESEARCH RESEARCH RESEARCH The Class A address 127.0. Each host on a network has a 32-bit address that is represented in dotted decimal format. 9.254 .168.H About 16 million 8 Class B 10 128–191 N.H 254 24 Class D 1110 224–239 H. B.1.H.168. Table 27-6 shows a network and broadcast address example. or the address on a network used to reach all hosts on that network. Know those first 8 powers of 2 and you will be able to diagram an IP address as binary or decimal. Table 27-2 provides you with an example of an IP address represented in both dotted decimal and binary formats.1 to 192.H.1.N.1.2.535 16 Class C 110 192–223 N.N. C.5—The address for a network cannot be assigned to a host.06_1587131749_DAY27. and part represents the network.H.0.1.1.0 is reserved for the loopback. As shown in Table 27-4. and E IP Addresses Class Binary Start 1st Octet Range Network (N) and host (H) Octets Number of Hosts Bits in Network Address Class A 0 1–126 N. It might also be good to practice adding those numbers in various combinations. D.

0.0 to 172. This is also possible with a class C network.255. 9. ■ DHCP—DHCP does not require you to enter information for each host that you add to the network. 9. As IP addresses become scarce.0.3. you can increase the subnet mask by borrowing bits from the host portion and create multiple smaller networks.6 and 9. As the replacement for BOOTP. private or internal addresses are available as outlined in RFC 1918 and Table 27-7.255. If you have an entire class B network.06_1587131749_DAY27. the DHCP server can reclaim the address for other hosts. Let’s say hostA broadcasts an ARP request and hostD has the matching IP address. With IPv6.0.5—You can assign a static IP address to a host.168. 128-bit IPv6 addresses consist of eight 16-bit sections separated by a colon and represented in hexadecimal format. Three common methods that hosts use to obtain an IP address automatically are as follows: ■ Reverse Address Resolution Protocol (RARP)—Hosts can use RARP to associate a MAC address to an IP address.0.255.255 Class C 192. “Design a Simple Internetwork Using Cisco Technology”). and we will cover subnetting in depth on Day 22. it is possible that 128-bit IP version 6 (IPv6) addressing will become the leading protocol on the Internet. DHCP requires only that you to enter a range (or pool) of IP addresses for the DHCP server to lease to a host. the Internet has a potential 640 sextillion unique addresses.255 Class B 172. You have to add an entry to the database on the BOOTP server for each host on the network. so Address Resolution Protocol (ARP) finds a MAC address using the IP address.3. ARP occurs when a host has a destination IP address for a packet but needs to determine the MAC address to send the packet over the LAN.7—RARP finds an IP using the MAC address.0 to 10.255.0 to 192. Two hosts cannot have the same IP address on the Internet and expect traffic to route. or the host can dynamically acquire an address.31.255 9. ■ Bootstrap Protocol (BOOTP)—BOOTP is a way for a host to use UDP to obtain an IP address as well as router and server information. usually the router. Table 27-7 Private Network Addresses Class Address Range Class A 10.1–9.2.3.7—There are no networks in the world with 1 router and 16 million hosts.qxd 30 7/28/06 8:53 AM Page 30 31 Days Before Your CCNA Exam 9. 9. Class A networks are always divided.2. Servers and network devices that provide services to hosts should have a static IP so that the hosts can find them. A RARP server. HostD will . must be present for RARP to function.16. The same is true of a network of any size that does not need to use the address space it reserves.168. When the lease expires.6—Hosts that are directly connected to the Internet require a unique public IP address.2.3. or subnetted in smaller subnetworks.8—The IP address discussion to this point has been about 32-bit IP version 4 (IPv4) address- ing. For networks that are not connected to the Internet or that are using a proxy (covered on Day 20.

10. but each router that views and forwards the packet will strip and replace the Layer 2 destination MAC address to get the frame across the LAN. As a connectionless protocol. If a packet does not reach its destination. an upper-layer protocol will request retransmission.1. A circuit-switched connection sends packets in order across a physical or virtual circuit. A packet will maintain the same destination IP address as it travels across LANs. Packet-switched communication can send packets along different network paths to be sorted and sequenced upon arrival at the destination.1. which can be up to 64 bits . HostA can then add this information to its ARP table and send the packet with the MAC-IP pair.4—IP is a Layer 3 routed connectionless protocol. the router will recognize this and respond with its MAC address with the intent of forwarding the packet. Remember that a Layer 3 packet is encapsulated in a frame for Layer 2 transport across a LAN.06_1587131749_DAY27.qxd 7/28/06 8:53 AM Page 31 Day 27 31 respond with its MAC address. If hostD is not on the local LAN.1. Module 10 10.1–10. CCNA 1. IP is considered a best-effort delivery system because it does not verify that a packet has reached its destination.5—The following fields make up an IP packet: ■ Version—Defines the format of the packet ■ IP Header Length (HLEN)—Length of all header information ■ Type of Service—Importance level as assigned by an upper-layer protocol ■ Total Length—Length of the entire packet ■ Identification—The sequence number ■ Flags—Identifies if the packet can be fragmented and if it is the last piece of a fragmented packet set ■ Fragment Offset—Used to assemble packet fragments ■ Time to Live (TTL)—The number of hops a packet can travel before being discarded ■ Protocol—Upper-layer protocol such as TCP or UDP ■ Header Checksum—Used to check the header ■ Source Address—IP address of sender ■ Destination Address—IP address of intended recipient ■ Options—Support for options like security ■ Padding—Used to keep the IP header a multiple of 32 bits ■ Data—Encapsulated information from upper layers. IP is a packet-switched process.

CCNA 2.1.06_1587131749_DAY27. CCNA 2. which does not feature acknowledgments or sequencing and broadcasts segments. The ping command uses an ICMP echo request to verify connections and waits to receive an ICMP echo reply.2. Module 10 in CCNA 2 repeats information from Module 11 in CCNA 1 and adds the following information: ■ While a TCP connection is established using the three-way handshake.1–11.1. sliding windows.1–8. IP does not report errors in transmission.9—ICMP also sends control messages to tell hosts about network conditions. Here are two quick para- graphs to summarize what Day 31 covered. hosts use DHCP to obtain IP addresses. ICMP allows a router to send an error notification to the device that originally sent the packet.1.1. Code. Different types of control messages are as follows: ■ ICMP redirect/change requests—Allow a gateway to inform a host about a better route ■ ICMP timestamp messages—Allow a host to exchange time information with a remote host and identify the delay across the network for time synchronization ■ ICMP source quench messages—Allow a gateway to notify a host if the network is congested and to temporarily slow transmission Hosts can also use ICMP to obtain an IP address to discover the subnet mask and to discover a router.2. positive acknowledgement. The TCP/IP transport layer creates a session between hosts using segments as the PDU and either standard ports (1023 and below) or nonstandard ports (above 1023). SNMP on port 161. the real flow control happens at the transport layer with TCP. and Telnet on port 23.2. If a router cannot deliver a packet. it is possible that a 1337hax0r (elite hacker) could send a number of SYN requests from a nonexistent IP address . This is the job of the Layer 3 protocol Internet Control Message Protocol (ICMP). Module 8 8. In today’s networks. ICMP messages start with Type.7—Didn’t we already cover Module 11 on day 31? Yep. and RIP on port 520. The TCP/IP transport layer can also use the connectionless UDP protocol.6—Although ICMP can send source quench messages. it will provide an ICMP destination unreachable message with a specific code to identify why the destination is unreachable. Examples of protocols that use TCP are TFTP on port 69.9—As mentioned previously.qxd 32 7/28/06 8:53 AM Page 32 31 Days Before Your CCNA Exam CCNA 1. 8.2. and segment sequencing.1–8. FTP on port 21. The TCP/IP transport layer can use TCP as a connection-oriented protocol. and Checksum fields. Module 10 10. Examples of protocols that use TCP are HTTP on port 80. Module 11 11. which features a three-way handshake.1–10. ICMP packets that cannot be delivered do not generate their own error messages to avoid congestion.

Second Edition (ISBN: 1587200791) might help you to refine this knowledge. and dynamic ports (49152 to 65535).06_1587131749_DAY27. IP address assignment occurs at Layer 3. It is important to understand the hierarchy and grouping of Layer 3 IP addresses and networks as well as the Layer 4 flow control and reliability of TCP. These repeated requests could cause a device to wait for an acknowledgement and use all of its resources. ■ A host can provide services simultaneously on two different ports. ■ Port number assignment occurs at Layer 4 of the OSI model. registered ports (1024 to 49151). Software exists that can recognize and repel such an attack. An example might be a web server that provides HTTP access on port 80 at the same time as Telnet access on port 23. ■ A more concise definition of port number ranges includes well-known ports (0 to 1023). Pages 123–145 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. and MAC address assignment occurs at Layer 2. ■ The process in sliding windows where TCP requests that a host resend information is called positive acknowledgement and retransmission (PAR).qxd 7/28/06 8:53 AM Page 33 Day 27 33 to this host. . exam #640-801). Summary From the initial ARP request to find a destination IP address to the last acknowledgement of a TCP segment. This type of denial-of-service (DoS) attack could prevent a device from responding to legitimate requests. the TCP/IP process assists Internet communication worldwide. Ignore the subnetting questions until after Day 22.

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and can contain a reduced version of the IOS for troubleshooting. ■ Interfaces—Connections from routers to other devices for networking and management. the engine of any network is its hardware.1—The internal components of a router are as follows: ■ Central processing unit (CPU)—Runs instructions from the operating system. FDDI. The CPU bus is used specifically for the CPU to transfer data to memory and back. including initialization. routing. and where interfaces temporarily store packets that the router is forwarding.2 and 1. and Token Ring technologies connect to a LAN interface.07_1587131749_DAY26. Module 1 1.2. ■ Buses—The system bus is the internal means of communication between the CPU and other internal components.7—The following list describes the three ways (aside from power) that you can physically connect to a router: ■ LAN connections—Ethernet. ■ Flash—Stores the full Cisco IOS software and can be upgraded with single inline memory modules (SIMMs) or a Personal Computer Memory Card International Association (PCMCIA) card. CCNA 2. The RAM can be upgraded with dual inline memory modules (DIMMs). On this short day you could definitely knock out another practice CCNA test when you have finished reading. RAM loses all data when the router is powered off. 1. ■ Random-access memory (RAM)—Where the router stores routing table information and the running configuration. The ROM can only be upgraded by replacing the actual chip. Modules 1 and 2 from CCNA 2 describe the various bits and pieces that make up network devices and how Cisco IOS software works with the hardware.3–1. loads the IOS.1. .2. ■ Nonvolatile random-access memory (NVRAM)—Stores the startup configuration and does not lose data when the router is powered down.2. and interface control.qxd 7/28/06 8:53 AM Page 35 Day 26 Describe the Components of Network Devices Although protocols and software determine the logical layout and provide instructions for network processes. You need a straight-through cable to connect a router to a switch and a crossover cable to connect a router directly to a computer or another router. ■ Read-only memory (ROM)—Holds the ROM monitor. ■ Power supply—Can be modular and supplies power to the router. which runs hardware diagnostics.

The service provider uses the DCE device to set clocking on the connection. which can be a channel service unit/data service unit (CSU/DSU) or a modem. Once you are logged in. ■ mz refers to the image location/compression. Typically. which is RAM/zipped.qxd 36 7/28/06 8:53 AM Page 36 31 Days Before Your CCNA Exam ■ WAN connections—If you choose to connect to a WAN.1. The following list explains the components of the Cisco IOS image name C2600-is-mz: ■ C2600 refers to the platform. the service provider will use a data circuit-terminating equipment or data communications equipment (DCE) device.4—Software compatibility with hardware comes into play when deciding to upgrade the Cisco IOS image on a router. You can look at this information in the CLI under user EXEC mode by typing show version to see the existing image name. Module 2 2.1. A quick and almost poetic way to remember the standard terminal configuration is to recall 9600-8-none-1-none. You can also configure a router by dialing to a modem connected to the AUX port. which is Cisco 2600 series. ■ is refers to the feature set. CCNA 2. you connect physically to gain access. and amount of flash memory. It is important to check your router to make sure that it has enough RAM and flash memory to support a new IOS image.1. then the feature set. ■ Management ports—Serial EIA-232 interfaces provide an out-of-band way to connect a terminal to the router and troubleshoot in a text-based session. The prompt is a > or ROMMON> ■ Boot ROM—A paired-down version of the IOS used to copy a new image to flash memory ■ Cisco IOS—The full Cisco IOS image stored in flash .3—You can manage a router in a text-based terminal using a command-line interface (CLI). you can use a rollover cable and a terminal emulation program (such as HyperTerminal) on a desktop computer to connect to the console port and manage a router. the CLI has two key modes: ■ User EXEC mode does not allow configuration changes and is represented by the hostname> prompt. amount of RAM. but once networking and virtual terminal access is configured you can also telnet to a router. to connect to your router as the data terminal equipment (DTE) device. An IOS image is named using a format that identifies first the platform. it can enter three different operating environments. and lastly where the image will run and if it uses compression.5—When you start a router. Initially.1.07_1587131749_DAY26.1–2. 2. which is IP Plus. as follows: ■ ROM Monitor (ROMMON)—Used for password recovery and diagnostics. 2. ■ Privileged EXEC mode gives you administrative access to all the configuration modes and is represented by the hostname# prompt.

2. a TFTP server.07_1587131749_DAY26.2. it first performs a power-on self test (POST) and then it loads a bootstrap and initializes the Cisco IOS image from flash. Once the IOS image is loaded. 2.2—A router has an LED light next to each interface that should blink to show activity if the interface is working properly. If there is no configuration file in NVRAM. to take a quick practice CCNA exam today if you have time. the IOS software starts the setup dialog. It might also help to look at many of the questions in pages 199–205 and 259–274 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Once you have everything connected. the IOS software searches for a TFTP server to load the configuration file. If there is no TFTP server. exam #640-801).2.qxd 7/28/06 8:53 AM Page 37 Day 26 37 2. Summary Your experience with actual routing hardware from the Academy and knowledge of how the software and hardware in a router relate will help with any CCNA questions covering this objective. The location of the IOS image can be specified in the configuration register. you use the RJ45 connector on one end of your console cable and the RJ45 to DB-9 adapter and serial COM port on your desktop. of course.2. open HyperTerminal and make sure that the settings are 9600-8-none-1-none.4—For a console TIA/EIA-232 port connection on a router. it loads the configuration file from NVRAM. or ROM. Next to the AUX port is an OK LED that illuminates when the system has initialized. . Second Edition (ISBN: 1587200791) and.1—When a Cisco router powers up.

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A frame that exceeds the maximum legal frame size causes a network diagnostic tool to report jabber on the connection. the router checks each packet that it processes against the ACL. A remote collision is likely the result of a local collision on the other side of a hub or repeater. A runt is a frame that is less than the minimum size of 64 octets. “Describe Network Communications Using Layered Models.2—If you configure an ACL on a router.1.08_1587131749_DAY25. “Implement an Access List.2. upper layer protocols. . ■ Remote collision—Occurs when a frame is too small. Module 6 from CCNA 1 and Module 11 from CCNA 2 describe collision detection and Layer 3 ACLs. ■ Late collision—Occurs after the first 64 bits of data have been transmitted for a frame.” and Day 3.” Day 10. and port number. Module 11 11. If two hosts attempt to transmit at the same time. As an administrator.2.1.8—The following are three main types of collisions that can occur on a network: ■ Local collision—Occurs when a network card notices that the receive (Rx) wires detect a signal at the same time the transmit (Tx) wires attempt to send data. You will cover ACLs again on Day 19. If a frame does not match its own frame check sequence (FCS). An ACL can match a packet by source.2. 6.” CCNA 1. Key points to remember about an ACL include the following: ■ To revise an ACL.” a host listens to find out whether the network is available and then transmits data. destination.qxd 7/28/06 8:53 AM Page 39 Day 25 Evaluate Rules for Packet Control The rules of Carrier Sense Multiple Access/Collision Detection (CSMA/CD) at Layer 2 and access control lists (ACLs) at Layer 3 help control how data can be sent across a network. you can assign one outbound and one inbound ACL per port for each protocol. a collision occurs and both hosts transmit until all devices have detected the collision. this is considered a cyclic redundancy check (CRC) error. The repeater would only regenerate a fragment of the collision and not the simultaneous Tx and Rx. These frames are usually collision fragments. “Troubleshoot an Access List. The router stops at the first match and does not check any other statements. The Layer 2 network card cannot recognize this type of collision and must rely on the upper layers to request retransmission. ■ A router checks ACL statements in the order in which the ACL rules have been entered in the configuration.1 and 11. “Develop an Access List to Meet User Specifications.6–6. ACLs can provide instructions for a router to accept or deny a packet. you must delete and recreate the entire ACL. CCNA 2. As discussed on Day 31. Module 6 6.2—CSMA/CD provides the rules for how a device can communicate on an Ethernet network. All hosts then use the backoff algorithm to wait a random amount of time before attempting to retransmit.

A binary 1 says that the bit can be ignored. but remember that you need to add a permit statement at the end if you want a packet that matches no specific statements to be forwarded. 11. who is sending the packet.00000001. ■ Extended—With an extended ACL.00000111 Wildcard Mask 0. by looking at the destination address).1.2.3—When you create an ACL.0. . you need to choose to make a standard. protocol.10101000. This allows the extended ACL to filter the traffic by looking at where it is headed (that is.08_1587131749_DAY25. The wildcard mask 0.1–11.00000000. 0.4—With a wildcard mask you can tell the router exactly what IP address or IP address grouping you want to filter.1.168. but it can look at who sent it.00000001.0.1. ■ Named—Named ACLs do not use a range of numbers because the name is the identifier.1. Always consider a wildcard mask in binary form. and port.2.255.0 11000000.0.qxd 40 ■ 7/28/06 8:53 AM Page 40 31 Days Before Your CCNA Exam At the end of every ACL there is an implicit deny that drops any packets that did not match an entry. but you can add statements only to the end of a named ACL. Extended ACLs use the number range 100 to 199.2. Do not look for a relationship between wildcard masks and subnet masks. A binary 0 in a wildcard mask says that the bit should be matched.168.168.0. Table 25-1 provides an example.11111111 Result 192.4—You should put an extended ACL as close to the source of the traffic you are filtering as possible. Named ACLs can be configured as standard or extended ACLs.1.10101000. Named ACLs can be altered without deleting the entire ACL and recreating it.00000000. We will cover configuration on Day 10.7 11000000.0.255 00000000. You should put a standard ACL as close to the destination of the traffic you are filtering as possible. destination. the ACL must match the range 192. extended. You pair a wildcard mask with an IP address and use binary to identify what part of the address should be matched. you can check the source.00000000 *A 1 means ignore. A standard ACL cannot look at where the packet is going. wildcard masks serve an entirely different function from subnet masks. 11.0.168.0 states that the ACL should match the entire host. and a 0 means match Using the information in Table 25-1. The following key points about each should help you choose wisely: ■ Standard—This type of ACL uses the number range 1 to 99 and checks only the source address—that is.0 to 192. 11. Table 25-1 A Wildcard Mask to Identify What an ACL Should Match Decimal Binary* IP Address 192. or named ACL.0 can also be represented by the term any or host in an ACL. A wildcard mask is not the opposite of a subnet mask and serves an entirely different function.

qxd 7/28/06 8:53 AM Page 41 Day 25 41 Summary Today you reviewed how a network can control the flow of data at Layer 2 with CSMA/CD and at Layer 3 with ACLs and wildcard masks. You may also want to read through pages 456–467 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. ponder this question: Should ACLs give you more control over a network or lessen the need to control a network? Taking a Networking Academy CCNA curriculum practice test will help you make this assessment. and 3. In the meantime.08_1587131749_DAY25. exam #640-801). Second Edition (ISBN: 1587200791). You will review ACL theory and configuration on Days 19. 10. .

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Module 2 2.1. 3.7. WAN protocols. Module 1 1. Routers. Module 1 from CCNA 2.09_1587131749_DAY24. and Modules 2. modems.1. 1. or E3. WANs often provide access over serial interfaces at lower speeds than a LAN.2. and routers often act as a gateway from your LAN to a WAN.qxd 7/28/06 8:54 AM Page 43 Day 24 Evaluate Key Characteristics of WANs A WAN connection allows you to link office. The phone company will ask you to connect your router.1. which can also be referred to as customer premises equipment (CPE) and the data terminal equipment (DTE).2—In CCNA 2 Module 1.7—WANs operate over a large.7—Imagine that your box of connectivity equipment has just arrived in the mail and it is time to connect to the WAN. digital subscriber line (DSL). You now need to be familiar with a few new WAN connectivity terms. Your DTE will likely connect through a CSU/DSU (could be a modem) as the provider’s data circuit-terminating equipment (DCE). Today you quickly review WANs. CCNA 1. CCNA 4. Frame Relay. you connected to the WAN and can now surf happily. WAN connection speeds can range from bits per second to gigabits per second in full duplex. and 5 from CCNA 4 discuss the key characteristics of WANs.1. or central office (CO). A common physical connection type for a DCE/DTE interface is a High-Speed Serial Interface (HSSI). Module 2 2. T3. You should know that you are connected to the provider’s nearest exchange. CCNA 2. Synchronous Optical Network (SONET). and 1. and WAN connections and then further explore WAN characteristics on Day 18. T1.3.2. “Choose WAN Services to Meet Customer Requirements.4—When you design a WAN.1. The connections and protocols specific to a WAN operate at OSI Layers 1 and 2. The port in your building that the phone company installed is called the demarcation point.1. Integrated Service Digital Network (ISDN). and the provider will set the clocking with the DCE. and communication servers play an important role in WAN design.” Module 2 from CCNA 1.1 and 2. 1.1. You can connect to a WAN using a modem. you will almost always coordinate with a com- munication service provider such as a local phone company. The cabling between you and the CO is often called the local loop or last mile. These physical and data-link standards and protocols are different for a WAN than for a LAN. E1. 4. school. Your HSSI connects to a CSU/DSU to provide proper . or private LANs across a large distance. geographically separated area.

it is called a permanent virtual circuit (PVC). Frame Relay switches create a virtual circuit (VC) between communicating hosts that exists only when the frame is being transferred.1. Table 24-1 WAN Physical and Data Link Layer Standards Physical Data Link EIA/TIA-232 64 kbps Point-to-point Cisco HDLC. 2. The phone system is considered a circuit-switched system.1. An HDLC frame starts and ends with a flag field. You can refer to a temporary virtual circuit as a switched virtual circuit (SVC).3—Table 24-1 displays the physical layer and data link layer standards for a WAN. PPP. A data field and FCS field follow.qxd 44 7/28/06 8:54 AM Page 44 31 Days Before Your CCNA Exam transmission of the signals over the link.4—A WAN connection uses a Layer 2 frame to encapsulate data.21 Synchronous digital 2. ■ Information frame—This frame holds data. 2. 2. LAPB EIA/TIA-449/530 Up to 2 Mbps Packet switched X. Following the starting flag field is a header field that includes the address. PPP and Cisco HDLC have an extra field that identifies the network layer of the encapsulated data.1. Frame Relay EIA/TIA-612/613 HSSI up to 52 Mbps Circuit switched ISDN V.09_1587131749_DAY24.35 48 kbps X. you can use a dedicated circuit and buy a fractional T1/E1 through T3/E3 or DSL or you can instead choose a switched circuit as one of the following: . A phone call requires continuous connectivity. The most common WAN encapsulation uses the HDLC standard. For data communication.25.1. and the frame ends with a flag field. A connection that shares capacity by switching packets for many nodes is called a packet-switched network (PSN). control. The Internet is an example of a connectionless PSN where each packet contains full addressing information. the exchange of the local carrier switches circuits to create a continuous circuit between you and the person you are calling. A modem can also serve this purpose by modulating and then demodulating the signal in order to pass digital information over an analog line. it is possible for many computers to share a connection and take turns requesting and receiving data as packets. ■ Supervisory frame—This frame controls data frame flow and can request retransmission if an error occurs.5—When you make a phone call. and protocol field. When a virtual circuit needs to exist forever. The control field identifies one of the following three types of frames: ■ Unnumbered frame—This frame is for line setup messages.6—To connect to a WAN. Frame Relay is an example of a Layer 2 WAN connection-oriented PSN where the route is determined by switches and each frame carries an identifier called a data-link connection identifier (DLCI). but a person who surfs the Web only needs to connect in short bursts to get and receive new information.

1.1—Interesting traffic could be defined in many ways. You can define a dialer-list on a Cisco router that tells the router what traffic should cause it to bring up a DDR link. The call with ISDN is faster than a modem.1.4—WAN serial communication requires that frames are sent one bit at a time over the wire.2. the network of Frame Relay switches moves the data to its destination.qxd 7/28/06 8:54 AM Page 45 Day 24 ■ Circuit switched in the form of ISDN or the plain old telephone service (POTS) ■ Packet switched in the form of X.1. Usually you subscribe to a network of trunked Frame Relay switches owned by a public carrier. . connection-oriented. HDLC encapsulating. and EIA/TIA-530. the router sets up the call and all traffic will be sent over the link until no more interesting traffic is sent and the idle timer timeout period completes. but in the context of dial-on-demand routing (DDR) interesting traffic is network activity that causes a router to connect to a network.1. Module 5 5. This digital connection allows you to exceed the 56 kbps bandwidth barrier of an analog connection. ISDN bearer (B) channels carry data at 64 kbps for each channel. CCNA 4. Module 3 3.3. A CSU/DSU typically is defaulted to auto sense it from the line. your router is the DTE and the provider allows you to connect to the DCE. Frame Relay would be a good choice. A router that is set up for DDR will receive packets and first check to see if the packets should be forwarded to the DDR link. If the packets fulfill both conditions. CCNA 4. CCNA 4. data link layer WAN technology. V. X.1—Local carriers use ISDN to provide a digital connection on the local loop for a subscriber. The ISDN delta (D) channel is used to set up the call and for signaling. Your DTE connection to the CSU/DSU will be through a serial connection using one of the following standards: EIA/TIA-232. and if so. you can save money if you request an SVC instead of a PVC. Serial communication standards include RS-232-E.7. 4. EIA/TIA-449. V.35. We will cover more of these terms on Day 18. the provider can allow you to share a physical link with other subscribers.1—If you were asked to name one packet-switched. check to see if they meet the criteria for interesting traffic.1 and 3. and HSSI. With an SVC. Frame Relay switches act as a DCE for a router. and the ISDN connection allows for a PPP-encapsulated link. Both a modem and a CSU/DSU can function as DCEs and are the entrance point to the service provider network.35. Module 4 4.21. Modems auto-sense the clocking from the service provider line. but may need to be configured. As mentioned in “CCNA 2.25 or Frame Relay ■ Cell switched as Asynchronous Transfer Mode (ATM) 45 If you choose packet switching and if your bandwidth requirements are low. Once the frame is forwarded from the DTE router to a Frame Relay switch. Module 1” under 1.09_1587131749_DAY24.

The routers on LAN1 and LAN2 operate as Frame Relay access devices (FRADs).1. The phone company uses its Frame Relay switches to then establish a packet-switched PVC across town for your two LANs. Your Notes . You learn more about these key WAN characteristics on Day 18. and types of WAN connections. First you call the phone company and connect your LAN1 router to their nearest Frame Relay switch. Summary Today you reviewed a comprehensive definition for a WAN. LAN2 will also have a DLCI that identifies it on the Frame Relay network.qxd 46 7/28/06 8:54 AM Page 46 31 Days Before Your CCNA Exam 5. including its relation to the OSI model. If you have CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.2—You want to connect LAN1 to LAN2 across town using Frame Relay. Second Edition. Your LAN1 router will have a unique DLCI that identifies it on the Frame Relay switch network.09_1587131749_DAY24. You then connect the LAN2 router to a nearby Frame Relay switch on the same phone company network. look over pages 488–510. exam #640801).

10_1587131749_Pt2.qxd 7/28/06 8:54 AM Page 47 Part II 23–18 Days Before the Exam— Planning and Design Day 23: Design a Simple LAN Using Cisco Technology Day 22: Design an IP Addressing Scheme to Meet Design Requirements Day 21: Select an Appropriate Routing Protocol Based on User Requirements Day 20: Design a Simple Internetwork Using Cisco Technology Day 19: Develop an Access List to Meet User Specifications Day 18: Choose WAN Services to Meet Customer Requirements .

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These terms include the following: ■ Bus—All devices connected to one arterial cable ■ Ring—Each host connected to two other hosts forming a ring ■ Star—All hosts connected to a hub or switch ■ Extended star—Hosts connected to a hub or switch that is in turn connected to a hub or switch ■ Hierarchical—Hosts connected to a hub or switch that is connected to another host or switch forming an extended star that is then connected to a proxy that handles traffic ■ Mesh—A direct physical link from each host to every other host 2.11_1587131749_DAY23. printers.1. Network protocols control the type of connection. and so on).5 and 2.1. networking media. and 10 from CCNA 1. Key network devices that glue a LAN together include the following: ■ Network interface card (NIC)—Connects the host to a network and contains a MAC address ■ Repeaters—Simply regenerate the signal ■ Active hubs—Regenerate the signal and have multiple ports ■ Bridges—Two ports that maintain a MAC address table for hosts ■ Switch—Multiple ports that maintain a MAC address table for connected hosts ■ Routers—Connects a LAN to a WAN 2. CCNA 1. 8. 5. Module 1 from CCNA 2.1.6—Networks need a set of rules to determine how they communicate. End-user devices (computers. and Module 5 from CCNA 3. The most common LAN technologies are Ethernet. These rules are defined as protocols. and how to handle errors.1. Module 2 2. hubs. peripheral devices. and so on) and network devices (cables.4—The terms to describe the physical topology of a network help you to explain how all of the devices are actually connected. how data is transferred.3—Networks contain two main types of devices. . and FDDI. and network devices make up the main parts of a LAN. 9. NICs. Computers. Important sections of the Cisco Networking Academy curriculum that cover LAN design are Modules 2.qxd 7/28/06 8:54 AM Page 49 Day 23 Design a Simple LAN Using Cisco Technology Previous days and topics about LANs spill together into LAN design with an additional focus on the Cisco three-layer hierarchical model. Token Ring.

A bridge can learn the MAC address of network hosts and determine whether or not to pass the signal to the separate segment. the WLAN is in one collision domain (similar to a hub). and use twisted pair (100 meter limit) as the media for transmission. 5. A hub does little beyond concentrate the cables in a LAN to a central point. 5. Common technologies include Token Ring.1. only three (3) of those segments can have hosts attached. a hub to a hub.1.1—The physical layer of a LAN focuses on the media (actual cables and technology) used to connect the machines and send information. 802. If both ends of the cable are wired the same. 1000BaseT implementations are 1000 Mbps. and 802. 5. All devices are still in the same collision domain.3z for 1000 Mbps.6—A repeater strengthens a signal to allow for greater cable and network distances. both A or both B. This kind of cable allows you to connect a switch to a switch. optical fiber. be sure to follow the 5-4-3-2-1 rule.1. you have created a crossover cable. The IEEE specifications for Ethernet are 802. baseband. or a router to a PC. a PC to a PC.9—Bridges move beyond that barrier of simple. Because all networking devices see all signals. You can use this kind of cable to connect a switch or hub to a router. This EIA/TIA-specified.1. Ethernet is implemented at the 100 Mbps (Fast Ethernet) level with Gigabit Ethernet as a backbone solution. you have a straight-through cable. Any group of devices that can cause a collision by attempting to communicate at the same time is in the same collision domain.7—Repeaters have just two ports and serve the purpose of doubling the length of a cable. and two (2) of the segments have no hosts on one (1) big collision domain. FDDI. A hub is a multiport repeater. 5.3—Details about the type of Ethernet implementation can be deciphered from the TIA/EIA standards.1.2—Ethernet was first implemented by Digital.3u for 100 Mbps. Module 5 5.3 for 10 Mbps. or a hub to a PC. Category 5 unshielded twisted pair (UTP) carries most LAN signals today. Bridges have only two ports. A network can only have five (5) segments connected with four (4) Layer 1 and Layer 2 devices. If you wire A on one end and B on the other end (or vice versa). . Intel.11_1587131749_DAY23. and Ethernet. Typically. 5. 5. a router to a router.5— At the end of an Ethernet cable is the RJ-45 connector. Improperly set up wireless LANs (WLANs) can have security risks. WLANs are predominately connected using radio frequency (RF) to communicate between transceivers (devices that have both a transmitter and a receiver). a switch to a hub. This will change as the cost to implement Gigabit Ethernet drops. clip-sporting piece of plastic comes in two flavors: T568A and T568B. and wireless as well. but because the price of switches has decreased. but signals can be transmitted through coaxial cable. Cost used to be a primary factor when deciding between a hub and switch.1. eightwire.qxd 50 7/28/06 8:54 AM Page 50 31 Days Before Your CCNA Exam CCNA 1. baseband. senseless signal sending. 10Base5 implementations are 10 Mbps. Save that crossover for your old stuff.1.8—LANs can be connected using wireless signals. and Xerox (DIX). are auto-sensing and therefore allow use of a straight-through cable where you once needed a crossover. cost is no longer an issue. a switch to a PC. and have a maximum length of 500 meters over coaxial cable. Many newer devices.1. If you are going to extend your LAN to its absolute maximum. however. 5.

but a switch has many ports. In order to begin filtering. The best and most adventurous way to learn this advice is through practical experience. the bridge can determine whether or not to forward traffic between segments. 5. they cannot send data at the same time or a collision will occur. The NIC is considered a Layer 2 device because it carries the MAC. 8.1. switches cause delay when they wait to learn a destination MAC address. To extend a network with a repeater or hub increases the potential for collisions. so each port on a switch is its own collision domain. Once all or many of the devices have communicated over the network. bridges. so an expert administrator and/or patient users prove necessary for the implementation of a server/client network.1. 8. When the number of hosts exceeds ten.13— Using the client/server model in large networks makes sense because a central server can control host authentication. The MAC address that switches.11—The network interface card (NIC) connects the host to a network. Point-to-point connections connect only two devices. Each computer acts as a server and client. Outside of the speed limitations of the signal. Servers provide a central point of failure. CCNA 1. Switches communicate with each other to prevent loops. The potential for collisions increases with the increase in hosts.1. Module 8 8.1. . A switch works like a bridge with many ports. use circuits to process the signal. and routers use to identify LAN hosts is burned on the NIC. and use software to determine where to forward traffic. This delay on a network is defined as latency.2. 5.1— When many devices use the same medium.2—A bridge initially does not know any MAC addresses on either of its segments.12—Peer-to-peer networks (ten or fewer computers) allow users to control access and resources individually.1.3—Switches can learn the source and destination of traffic and create a virtual circuit between two hosts on a network. a bridge listens to traffic on both of its ports and builds a table that associates MAC addresses with ports.4—It takes time for a signal to travel across the media. This virtual circuit can then operate in full duplex and double the bandwidth. Although routers identify hosts on a LAN using the MAC address. and each port on a switch is its own collision domain or microsegment. An example of a point-to-point connection is a WAN link using a modem.1. a router uses the host’s Layer 3 IP address to forward data between networks. and back up all vital network data.1. File and print sharing are the common configurations on a peer-to-peer network. Switches also use content addressable memory (CAM) to quickly store and retrieve MAC table information and application-specific integrated circuits (ASICs) to speed up the process of filtering and forwarding traffic. allowing access to its resources while accessing other peer resources. Switches are able to create virtual circuits between devices that wish to communicate.1 and 8. 8.1.qxd 7/28/06 8:54 AM Page 51 Day 23 51 5. or the ability to divide switch ports into their own segment. Configuration options in the software of a switch allow for the creation of virtual LANs. 5. it is wise to implement a server and centralize access to resources for security and organizational purposes.11_1587131749_DAY23. file and print access.10—A switch is able to learn the MAC address like a bridge.

2—If you can increase collision domains on a network. This is called an Address Resolution Protocol (ARP) request. a Class C addressing scheme often .2. routers. but routers also look at frames and drop any frames that do not have their destination MAC address. then you can improve network per- formance.qxd 52 7/28/06 8:54 AM Page 52 31 Days Before Your CCNA Exam 8. For LANs. It is important to follow the 5-4-3-2-1 rule described previously in the section “CCNA 1. LANs are also designed to communicate with other LANs through routers. An ARP request is one example of a Layer 2 broadcast. 8. Module 5” under 5. 9.1—NICs provide a host with a MAC address and the ability to express a unique identity to local switches. Class B addresses use the first two octets to identify the network and the last two to identify the hosts.5—To prevent ARP requests from broadcasting to all devices on a network every time a host needs to resolve an address. Routers use IP addresses and MAC addresses to filter and direct traffic. it initially broadcasts a request for that host’s MAC address. This kind of performance might have been okay for network games in the early ’90s.4—When a host needs to locate another host. Broadcasts pass across all switches using the broadcast address 0xFFFFFFFFFFFF. 9. Class A addresses use the first octet for the network ID and the last three octets to identify the hosts. you use a router.3—Hosts on a LAN with duplicate IP addresses cannot communicate.11_1587131749_DAY23. The 32 ones and zeros in an IP address are divided into octets and represented in dotted decimal notation. CCNA 1. Routers are able to determine whether Layer 2 MAC broadcast traffic is destined for a host outside the LAN by looking at the IP address. the router will respond in order to receive and forward the traffic. 8.3—And how does one increase collision domains? Through segmentation with switches and routers.2. you just need general knowledge about address classes and how to implement them. IP addresses allow hosts to identify themselves by network and local location with a 32-bit address. All hosts must process and respond to this request. Routers operate at Layer 3 to forward data using the IP address. If the IP of the destination host is outside the LAN. Class C addresses use the first three octets to identify the network and the last octet to identify the host. Each host must have the same network address and a unique host address. and other network devices for Layer 2 traffic purposes. Switches can filter traffic destined for individual hosts and divide collision domains.2.2. Switches filter traffic by MAC address and keep local traffic local. but not so for the demands of today’s serious LAN clan. Each octet can only be a decimal number between 0 and 255.6 in order for a network (and network games) to function properly without excessive delay.1. Imagine a LAN party with 50 hosts connected with hubs.2. so a flat MAC addressing scheme is inferior to a hierarchical scheme using TCP/IP. a collision would occur and all hosts would be required to back off for a set amount of time. only one host could communicate at a time.4—For the purpose of designing a LAN. Each time two hosts attempted to communicate. 8. and routers can filter broadcasts and divide broadcast domains. Class D addresses are reserved for multicasts. Module 9 9.2.2. and Class E addresses are reserved for research. In a single collision domain.

0 to 10. The private ranges are as follows: ■ Class A: 10.0.3 ■ Host 3 is 192. 9.168. servers. .0 to 172.5—Dynamic Host Configuration Protocol (DHCP) is the most common way to allow hosts to obtain IP addresses automatically.2—Some network administrators of small networks manually provide all hosts with static addresses. At this point.2 ■ Host 2 is 192.168.2—Switches operate on the LAN to uniquely identify local machines by MAC address and regulate traffic between these hosts.168. If a host tries to communicate with a machine that is not on the LAN. It is a good idea to assign static addresses to network devices that other hosts must find on a regular basis. An example of how you might address a LAN with 3 hosts using a Class C addressing scheme is ■ Host 1 is 192.255 ■ Class B: 172. or host octet. If two interfaces connected to a network are assigned the same IP address. and a switch operates at Layer 2. or an administrator can statically assign the address. You will likely know when this type of administration does not fit your situation.1. the router steps in and responds for that otherwise unreachable host.168. and network printers.6—RFC 1918 states that there are reserved Class A.0 to 192. Module 10 10. and C address ranges for private LANs.2. A router operates mainly at Layer 3. The switch forwards the traffic for that host to the router.5—Many addresses are reserved for use outside of host identification. this could cause conflicts and render both connected interfaces unable to communicate. and the last address (all ones in the host section) is reserved for broadcasts.255 9.255. 9.0. and it is up to the router to use the IP address to find the host.0.255. the switch will search for that machine locally and find no matching MAC address.255 ■ Class C: 192.168.0.3. B.1—A host on a network can obtain an IP address automatically. The first address (all zeros in the host section) on a network is reserved for the network. 9.16.3. 9.255.31.2. such as routers.4 Notice how the first three network octets remain the same for the entire network and the last octet.255.1. identifies the host. the hosts on the network can use DHCP to obtain an address. CCNA 1.3.11_1587131749_DAY23.qxd 7/28/06 8:54 AM Page 53 Day 23 53 works well because you do not need more than 255 hosts.2. Once an administrator sets up a DHCP server and identifies a range of available IP addresses.1.

This structure can follow the TIA/EIA-568-A standards including your wiring scheme.11_1587131749_DAY23. include the logical topology and an addressing scheme to define the flow of the network. . Module 1 1. 5. you can use fiber optics as the backbone vertical cross-connects (VCCs) to IDFs and then distribute connections.1. Also document the financial and managerial structure of the network.qxd 54 7/28/06 8:54 AM Page 54 31 Days Before Your CCNA Exam CCNA 2.3—Actions that you can perform while designing a LAN are as follows: ■ Gather LAN requirements and expectations—Determine the skill level and attitude of the users as well as the demands put on the network by host hardware and software. 5. and 3 of the LAN—Provide a well-organized chart of the network.4—To design the OSI Layer 1 scheme for a simple LAN. you can place them in the intermediate distribution facility (IDF). At the network and data link layers. you can connect the switches to a patch panel and patch cables as horizontal cross-connects (HCCs) to the hosts.1. place them in the main wiring closet. The router connects through a straight-through cable to a hub or switch. data link. If your network also includes workgroup servers. Starting with a router connected to switches in your MDF. create a cut sheet to define location and installation of devices in the facility. 2. ■ Design OSI Layers 1. the use of fiber optics and Fast Ethernet is most common. At the physical layer. keep the following four goals in mind: ■ Functionality–The LAN has to allow users to accomplish their intended tasks. Module 5 5. CCNA 3. ■ Scalability–The LAN should support growth without a need to make any major changes.1.2. Category 5e UTP to connect from these wiring closets to the hosts. or main distribution facility (MDF). and physical layers of the LAN that can act as a road map for implementation. ■ Analyze the data you have gathered—Use data from the previous action to estimate costs and a timeline to implement the project.1. Use switches to segment collision domains and routers to filter broadcasts. From the IDFs. 5.1—When you design a LAN.6—The router is the connecting point for a LAN to other LANs or a WAN. ■ Manageability–You should be able monitor and maintain the network in order to keep a stable environment.1.2—If your network includes enterprise servers. ■ Adaptability–The LAN should have the ability to upgrade to accommodate future technologies. A router is most commonly connected to a LAN on its Ethernet or Fast Ethernet interface. you can use 10/100BaseTX. If your building exceeds the 100-meter limit for Category 5 UTP to reach all hosts.3 and 1. Find out quickly who can make decisions and spend money and what they want.

which provide an outline for the types of devices and connectivity necessary in a large network.2. You need a beefy OSI Layer 2 or 3 switch to handle the demands of the core layer.1. 5000. Routers commonly forward data based on IP addressing. if you have time. You could use Catalyst 2926G. exam #640-801). and design layers surface any time you design. you should use switches. You can divide Layer 2 switches into virtual LANs (VLANs) to separate networks at Layer 3.3 and 5. you can place appropriate switches in the MDF and IDFs. 2950.5—As the backbone of the network. and access layers. and 5000 series switches at the access layer. ACLs. and 6000 families at the distribution layer.6—Layer 3 LAN design centers around the placement and configuration of routers on the LAN. Summary Networking devices. 3550.2.qxd 7/28/06 8:54 AM Page 55 Day 23 55 5. The core layer serves as the backbone reserved for high-speed transmission. provide microsegmentation. Routers can also act as firewalls and provide a WAN connection. logical structure. 2820.1. 5.11_1587131749_DAY23.2. distribution.2.4—The distribution layer handles packets and OSI Layer 3 policies so that the core layer remains fast and efficient. explain. To microsegment collision domains. 3560. and the Catalyst 6500. VLANs. The distribution layer divides the core layer from the access layer with policy.2. You could use Catalyst 1900. connect LANs. and divide broadcast domains between the LANs. Second Edition. These concepts also show up often on the CCNA. HCCs are direct to hosts and should balance with a faster VCC between wiring closets. Once you have determined how many ports you will need for all hosts and connections to the LAN. No access list implementation or packet manipulation occurs at the core layer. 5. and can be separated into VLANs. 5. but you need a router to communicate between VLANs. The use of hubs instead of switches increases the size of collision domains to all hosts connected and affects bandwidth. The access layer connects users and remote sites to the network. IGX 8400. 8500. Collision domain microsegmentation and MAC address filtering also occur at the access layer. 4000. 5.2—Access layer switches operate at Layer 2 of the OSI model. Redundant paths implemented with Ethernet or ATM characterize the core layer. This model consists of the core.5—Your OSI Layer 2 design will focus on how the LAN will forward frames. Switch ports have only two hosts per collision domain with a source and destination host. and Lightstream 1010 fit the bill. Browse through pages 13–66 of the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. 5. the core layer is designed to move packets as quickly as possible. . and aggregation in the wiring closet at the distribution layer protect the core layer from handling these functions. Distribution layer devices include OSI Layer 2 and Layer 3 switches. or document a LAN. you need to switch gears and focus on the Cisco Three-Layer Hierarchical Model.1—At this point.

11_1587131749_DAY23.qxd 56 7/28/06 8:54 AM 31 Days Before Your CCNA Exam Your Notes Page 56 .

and today you learn the topics that allow you to be flexible and creative with IP addressing design. . Notice that the IP address is made up of four sets of 8 bits (octets).12_1587131749_DAY22. Module 1 1. The main points necessary for today are outlined in Tables 22-3 through 22-5.168. Module 9 9. D. Table 22-1 shows the powers of 2 for an 8-bit binary number.10101000.00000111 CCNA 1. refer to Day 27.1–9. B.2. “Evaluate the TCP/IP Communication Process and Its Associated Protocols.qxd 7/28/06 8:54 AM Page 57 Day 22 Design an IP Addressing Scheme to Meet Design Requirements Day 27. public. C.5–1. and E IP addresses.2.2.2. Table 22-1 One Octet of an IP Address Bits and Powers of 2 1 1 1 1 1 128 64 32 16 8 Table 22-2 1 4 Decimal Equivalent 1 1 2 1 128+64+32+16+8+4+2+1 = 255 Binary-to-Decimal Conversion for an IP Address Numbering System IP Address Decimal 192. CCNA 1.8—On Day 27 you covered default address classes and reserved.” discussed basic IP addressing.00000001. If you are not sure how this conversion works. It is important to chop away at subnets and use advanced addressing to design a more efficient and secure network. and Table 22-2 shows an example of an IP address in both dotted decimal and 32-bit binary. Table 223 shows Class A.7—You cannot leave out binary in the quest to understand IP addressing. and private IP addresses.1. You will cover a quick review of the topics from Modules 1 and 9 from CCNA 1 and then learn new concepts in Module 10 from CCNA 1 and Module 1 from both CCNA 3 and CCNA 4.7 Binary 11000000.

3.H 254 24 Class D 1110 224–239 H.1.H About 16 million 8 Class B 10 128–191 N. B. divide broadcast domains on your network.535 16 Class C 110 192–223 N.0 is reserved for the loopback. and C default networks into smaller networks by identifying individual bits in the host portion as network bits.H 65.168.255 Class B 172.168.0 to 192.N.16.0.255.2—You can break up the Class A. Table 22-5 RFC 1918 Private Network Addresses Class Address Range Class A 10. and add security with access lists.1. You have the entire last octet to address hosts (minus the network and broadcast address).3.168. If you borrow bits from the host portion.H. and E IP Addresses Class Binary Start 1st Octet Range Network (N) and host (H) Octets Number of Hosts Bits in Network Address Class A* 0 1–126 N. 10.254 Table 22-5 lists the Class A.H. the subnet mask in both decimal and slash format.168. Table 22-6 provides the bits borrowed from the host portion.0. .3—A default Class C network has a subnet mask of 255.255.255 CCNA 1. Class B.0.0 192.255.H.12_1587131749_DAY22.255.1.H Multicast 28 Class E 1111 240–255 RESEARCH RESEARCH RESEARCH * The Class A address 127.1.168.255.168. and Class C private address ranges.0 192. Table 22-4 Reserved Network and Broadcast Address Example Network Default Class C Binary Host All 0s Network Address Binary Host All 1s Broadcast Address Useable Hosts 192.1.255 Class C 192. The term for this practice is subnetting.0 to 172. which are defined in the IETF RFC 1918. C. B. which allows you to efficiently use IP addresses.0.1 and 10. the subnet mask will reflect the bits that you have borrowed.qxd 58 7/28/06 8:54 AM Page 58 31 Days Before Your CCNA Exam Table 22-3 Class A.N. and to subnet the last octet of a default Class C.0. D.31.255 192.H. and you will have more networks but fewer hosts for each network.H.255.0.1 to 192.0 to 10.0. Table 22-4 shows an example of the addresses reserved on a network to represent the broadcast and the entire network. and the amount of networks and hosts.3.N. Module 10 10.168.

168. Module 1. You can determine all of the information in Table 22-6 by using the binary representation and the powers of 2.255.1.1.126 192.168.64 .1.0 with 2 Bits Borrowed (255.255.255 Remember that the subnetwork ID cannot be assigned to an interface.4—To continue with the example of 2 bits borrowed.1. Module 1. To find the amount of networks.3.192 . As an example. RFC 1878 (Dec.190 192.128 . so the last octet of the mask is the decimal representation of 11000000.” 10.168.192 Mask) Subnetwork Number Subnetwork ID Host Range Broadcast ID 0 192.168. The host range would fall between the network and broadcast addresses.5—You need to rely heavily on the use of binary representation and the 2^n–2 formula (unless you are using the zeros and ones subnets) when subnetting a Class A or Class B network.qxd 7/28/06 8:54 AM Page 59 Day 22 Table 22-6 59 Bits Borrowed and Corresponding Mask for a Class C Network Bits Borrowed 1 2 3 4 5 6 7 8 Mask 128 192 224 240 248 252 254 255 Slash format /25 /26 /27 /28 /29 /30 /31 /32 Total subnets 2* 4 8 16 32 64 N/A N/A Useable subnets* 0* 2* 6* 14* 30* 62* N/A N/A Total hosts 128* 64 32 16 8 4 N/A N/A Usable hosts 126* 62 30 14 6 2 N/A N/A *Refers to CCNA 3. If you look at the number of zeros in the mask 11000000.1–.191 3 192. In this case.1. This gives you an interval of 64. Use of the first and last subnets is discussed later today in the section “CCNA 3.63 1 192.) You have borrowed 2 bits from the last octet and changed them from host bits (0) to network bits (1).3. Make sure that you understand when you can use the all zeros and all ones subnets. you can use host bits available and apply the formula 2^n without subtracting 2. you can insert the number of bits borrowed into the formula 2^n–2 (unless you are using the all ones and all zeros subnets). the /26 network means that there are 26 bits total for the network portion.1.63–.1. . (Remember that a default Class C uses 24 bits.1. or 192. In this case. Using this interval. you can also determine the interval for the subnetworks using the mask.168.1. Table 22-7 provides an example of the networks and host ranges available for a default Class C network with 2 bits borrowed.12_1587131749_DAY22.193–.168.0 .168. 10. Table 22-7 Subnetworks for 192.168. 1995) started the use of all zeros and all ones for subnets.129–. The /25 subnet is now usable as well as the number of subnets listed in the total subnets row. your result is two networks available.127 2 192.254 192.168.62 192. you can place those remaining bits in the formula 2^n–2 and you will find that you have 62 hosts available per network. you can start with the zero subnet and then add 64 to identify your networks.

1–5.16. 1. (There would be 128 total.2.00000010.255 2 172.4—Consider the three subnetworks in use in Table 22-10 applied to a network with a serial point-to-point connection between two routers with 250 host LANs connected to each router.0 .2.16.0 .0 CCNA 3. a router uses the AND operator to determine the network and host portion of an address.0. but you may need to deal with higher powers of 2.1.3.qxd 60 7/28/06 8:54 AM Page 60 31 Days Before Your CCNA Exam It is technically the same as subnetting a Class C.254 172.7.16.0 Mask) Subnetwork Number Subnetwork ID Host Range Broadcast ID 0 172. routers can use subnet zero by default. Using VLSMs.0 with 7 Bits Borrowed (255.11111110.) Table 22-8 Subnetworks for 172.254.3 and 1.1–7.1–3.1. The no ip subnet-zero command enables use of these subnets in Cisco IOS software versions before Cisco IOS Release 12.255 3 172.255.1. Module 1 1.255 10. An example is to divide a Class C /24 mask to use the /30 mask for a point-to-point connection and then a /28 mask for a network with ten hosts.16.0.254 172.0.255 1 172. . Enhanced Interior Gateway Routing Protocol (EIGRP).255.00000000 1 AND 1 = 1 Result Mask 255.16. so you do not need to subtract 2 to determine usable subnets.0.1—You can efficiently use IP addresses by implementing variable-length subnet masks (VLSMs).00010000.16.1.11111111.0 .3.0 10101100.12_1587131749_DAY22.16. With subnetworks it is important that a router know the subnet mask for a network in order to forward the packet to the correct subnetwork. After Cisco IOS Release 12.2.6—As mentioned on Day 27.38 0 AND 1 = 0 IP address 10101100.254 172.16. Table 22-9 Using the AND Operator to Determine a Network Address AND Operator IP Address and Subnet Mask to Network Address 0 AND 0 = 0 IP address 172.1–1.0.16.6.2—As noted by the asterisks in Table 22-6. Integrated Intermediate System-to-Intermediate System (Intermediate IS-IS).2.00100110 1 AND 0 = 0 Subnet mask 11111111. and Routing Information Protocol version 2 (RIPv2) support VLSM.00000000 Network address 172.254.5.16. you can use the first and last subnets in conjunc- tion with VLSM.4.00010000. Static routes and only certain routing protocols such as Open Shortest Path First (OSPF).4.16. Table 22-8 provides a subnetted Class B network as an example with the first four subnetworks.254 172.6. Table 22-9 reviews the ANDing process with an address from subnetwork 1 in Table 22-8.1.0 .00000010. you can choose the subnet mask that best suits the number of hosts for each section of the network. 1.

80 as the source address for the packet on the Internet.1.2. Module 1 1.254 172.16.1.2. but for complicated networks it might help to find a VLSM chart on the Internet and use it to cross out used subnetworks. and hostA attempts to communicate with an Internet server with the address 128.0.qxd 7/28/06 8:54 AM Page 61 Day 22 Table 22-10 61 Subnetworks for 172.16.4 /30 0.9.16.5–0. Remember when you are using VLSM that your host ranges cannot overlap. Make sure that you do not later use a large subnetwork (an example would be 172. 1.255 Notice that the point-to-point link is flagrantly using 254 hosts when it only needs 2.0 /24 2.0.8.16.16.1–2.2.0. the following could happen with NAT: ■ HostA will send its packet with the inside local address of 10.16.16.2. VLSM and classless interdomain routing (CIDR) allow for more efficient use of IP address space and routing tables.0.1–2.0.0.1–1.16.5—If you use VLSM and keep your subnets sequential or grouped together.2.7 1 172. Using only NAT.1.0 space by using the /30 mask.5.0.2.2.16.0 with 8 Bits Borrowed (255.5 with its inside global address of 179.0 /24 for Table 22-11) that includes a small subnetwork you are already using.3—If you have designed a network using nonroutable private addresses (specified earlier in Table 22-5).0. a router can represent the group of subnets as one large subnet to other routers.6 172.254 172.2.255 This configuration leaves many available subnetworks in the 172.23.0.0 /24 0.16.1–1.0. ■ The router will send the packet to the Internet server’s outside global address of 128.255. your router has an interface on the Internet with the address 179.5. If you have an internal PC hostA with an address of 10. Table 22-11 Subnetworks for 172.1.255 1 172.0 Mask) Subnetwork Number Subnetwork ID Mask Host Range Broadcast ID 0 172.1–0. CCNA 4.23.16.80. you can represent an internal IP address as an external (real) IP address.16.16.1. This type of route aggregation.254 172.254 172.1–1.0. You can free up most of those hosts by implementing VLSM and using the networks outlined in Table 22-11.16.0. You can check host ranges for duplicates. you can still connect these internally addressed hosts to the Internet using network address translation (NAT) and port address translation (PAT). keeps routing tables small between networks.0.0.16.255. .8.1.0 /24 1.0 with VLSMs Subnetwork Number Subnetwork ID Mask Host Range Broadcast ID 0 172.0 /24 1.255 2 172.255 2 172.16.1. ■ The router will replace the source address 10. or summarization.254 172.0 /24 2.12_1587131749_DAY22.

but the ratio is still one to one. exam #640-801).0. but also helps you to understand and troubleshoot a number of OSI Layer 3 issues. PAT uses source port addressing to represent multiple private addresses with one Internet IP address. Overloading. RFC 1918. PAT. NAT can only map one Internet IP address to one private IP address. or assigning multiple private addresses to one Internet IP address.0. and good ol’ IP. CIDR. Your Notes . proves possible with NAT and PAT together. Summary Now you should be able to design a network that incorporates NAT. Second Edition. VLSM.qxd 62 ■ 7/28/06 8:54 AM Page 62 31 Days Before Your CCNA Exam When the router receives a reply from the Internet server. A pool of Internet addresses can be dynamically mapped to private addresses. it will look in its NAT table and see an entry that maps the packet from the server back to hostA’s inside local address of 10. This knowledge not only puts your best foot forward at a job interview. look over pages 141–146 and 475–480. Practice and research different methods and examples to help solidify your abilities with subnetting and VLSM.12_1587131749_DAY22.5. If you have the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.

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Day 21
Select an Appropriate Routing
Protocol Based on User
Requirements
CCNA objectives for today and Day 28, “Evaluate the Characteristics of Routing Protocols,” complement each other. Today you focus on comparing routing protocol features to perfect your ability
to pick the proper protocol. If you have completed Day 28 and can characterize routing protocols,
you should not have much trouble understanding the concepts behind the features. Today we first
outline the function of a routing protocol with information from CCNA 1 Module 10. You will
then review only the information that compares routing protocols from Module 6 of CCNA 2 and
Modules 1, 2, and 3 from CCNA 3.

CCNA 1, Module 10
10.1.1—Routing protocols allow routers to learn about available networks. Routed protocols provide addresses for hosts to communicate over a network. As a routed protocol, IP uses a subnet
mask to identify the network. Day 27 and Day 22 explained how a subnet mask allows a router to
identify a group of IP addresses as a network.
10.2.1—Routing occurs at OSI Layer 3. Routers look only at an individual address in order to

apply a netmask and then find the path to the network. Routers see networks, not individual
addresses. The individual IP address becomes necessary only to determine the final destination of
the packet. Other OSI Layer 3 routed protocols are Internetwork Packet Exchange (IPX) and
AppleTalk. NetBEUI is the most common nonroutable protocol.
10.2.2 and 10.2.3—As a switched LAN grows, it becomes necessary to segment the LAN with
routers. Routing and switching processes both forward data based on addressing, but switching
occurs at Layer 2 using the MAC address. The MAC address is unique to the LAN and allows the
switch to forward frames and maintain a flat table of MAC addresses without any specific organization. The router maintains a routing table of connected networks and uses the Layer 3 addressing
scheme to forward packets outside of the LAN and to other LANs. The hierarchical nature of
Layer 3 addresses allows the router to group and organize network knowledge. Additional examples of these Layer 3 routed protocols are Banyan VINES and Xerox Network Systems (XNS).
10.2.5–10.2.9—Day 28 presents most remaining information in Module 10 using summaries
from CCNA 2 Module 7. CCNA 1 Module 10 does add that routers determine network paths using
the following information from a routing table:

Protocol Type—The Layer 3 routed protocol

Next-hop association—The directly connected network or a network that the router has
learned about through a routing protocol

Routing metric —Used to determine the most efficient path

Outbound interfaces—Which interface to forward the packet for the specified route

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CCNA 2, Module 6
6.2.1–6.3.4—Table 21-1 and Table 21-2 review points about types of routing protocols covered in

Day 28 from CCNA 2 Module 6 with the addition of administrative distances for each routing
protocol.
Table 21-1 compares distance vector and link-state protocols.
Table 21-1

Distance Vector and Link-State Protocols

Distance Vector

Link-State

Routers send periodic updates of the
entire routing table to neighbors.

Routers send link-state advertisements (LSAs) to update other
routers only when there is a topology change.

Routers see only neighboring routers.

Routers use the LSAs to build a full loop-free topology of the
network, but this requires more memory than a distance vector
protocol.

Routers use a metric to determine the
cost path for a route and build a routing
table.

Routers use the Shortest Path First (SPF) algorithm and LSAs to
build a shortest path tree as well as a routing table.

Table 21-2 describes specific distance vector, link-state, and hybrid protocols.
Table 21-2

Routing Protocols

Protocol Name

AD

Type

Description

Routing Information
Protocol (RIP)

120

Interior distance vector

Broadcasts updates every 30 seconds and uses hop count as the metric with a maximum of 16

Interior Gateway Routing
Protocol (IGRP)

100

Interior
distance vector

Cisco proprietary protocol that
broadcasts updates every 90 seconds
and uses bandwidth, load, reliability,
and delay as a metric

Open Shortest Path First (OSPF)

110

Interior link-state

Nonproprietary protocol that
updates only when there is a change
in topology. OSPF uses cost as a
metric

Enhanced Interior Gateway
Routing Protocol (EIGRP)

90

Interior hybrid

Cisco proprietary protocol that uses
both link-state and distance vector
features and multicasts updates on
224.0.0.10. EIGRP uses the same
metrics as IGRP

Border Gateway Protocol (BGP)

20

Exterior distance vector

Used to route between autonomous
systems

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CCNA 3, Module 1
1.2.1–1.2.3—Table 21-3 compares RIPv1 and RIPv2.
Table 21-3

RIPv1 vs. RIPv2

RIPv1

RIPv2

Simple configuration.

Simple configuration.

Does not send subnet mask information in
the routing update. All subnets must have
the same subnet mask.

Sends subnet mask information with updates. Supports
VLSM and CIDR.

No authentication.

Supports MD5 authentication.

Broadcasts updates over 255.255.255.255.

Sends updates as multicasts over 224.0.0.9.

CCNA 3, Module 2
2.1.1–2.1.6—The following points are additional features of a link-state protocol:

Link-state protocols send hellos periodically to obtain information about neighboring routers.

When a network changes, a router will flood LSAs on a specific multicast address across the
specified network area.

LSAs allow the router to create a topological database of the network, use the Dijkstra algorithm to determine the shortest path for each network, build the shortest path tree, and use the
tree to build the routing table.

Flooding LSAs across a network can affect overall bandwidth on a network and cause each
router to recalculate a full topological database.

A network using a link-state protocol must be broken up into small enough areas to maintain
network efficiency and use routers with sufficient memory and processing power.

2.2.1–2.2.7 —OSPF includes these features:

OSPF is a nonproprietary link-state protocol that allows you to control the flow of updates
with areas.

OSPF allows more than 15 maximum hops, and large networks can be divided into areas.

OSPF areas communicate with a backbone area to reduce routing protocol traffic and routing
table size.

OSPF-enabled routers are true to their link-state definition in that they maintain a full loopfree topological database of the network.

Each OSPF-enabled router maintains a unique adjacency database that tracks only neighbor
routers.

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OSPF-enabled routers elect a designated router (DR) and backup designated router (BDR) as
central points for routing updates.

VLSM support, a bandwidth-based metric, a loop-free SPF tree, and rapid convergence
through LSAs are key features of OSPF.

OSPF routers that are connected on broadcast multiaccess networks such as fiber or Ethernet
or nonbroadcast multiaccess networks such as Frame Relay elect a single router to handle
updates called the DR. To avoid a single point of failure, they also elect a BDR.

OSPF hello packets typical to link-state protocols go out over the multicast address 224.0.0.5.
If the connection is broadcast or point-to-point, the hellos go out every 10 seconds; and if the
connection is nonbroadcast multiaccess (NMBA), the packets go out every 30 seconds.

CCNA 3, Module 3
3.1.1 and 3.1.2—Each of the following points identifies an EIGRP feature:

EIGRP and IGRP routing protocols can function seamlessly together on a network.

EIGRP also supports VLSM where IGRP does not. A router running only IGRP will see
EIGRP routes as IGRP routes.

As an advanced distance vector routing protocol, EIGRP uses functions from both link-state
and distance vector protocols.

Like OSPF, EIGRP collects multiple databases of network information to build a routing
table.

EIGRP uses a neighboring table in the same way that OSPF uses an adjacency database to
maintain information on adjacent routers.

Unlike OSPF, EIGRP uses a distance vector diffusing update algorithm (DUAL) to recalculate a topology.

EIGRP maintains a topology table that contains routes learned from all configured network
protocols.

The neighboring and topology table allow EIGRP to use DUAL to identify the best route, or
the successor route, and enter it into the routing table. Backup routes, or feasible successor
routes, are kept only in the topology table.

In the topology table, EIGRP can also tag routes as internal or external. Internal routes are
from inside the EIGRP AS, and external routes come from other routing protocols and outside
the EIGRP AS.

3.1.3 and 3.1.4—Advanced features of EIGRP that set it apart from other distance vector routing

protocols include:

Rapid convergence—EIGRP uses the DUAL finite-state machine (FSM) to develop a full
loop-free topology of the network allowing all routers to converge at the same time.

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Efficient use of bandwidth—EIGRP, like OSPF, sends out partial updates and hello packets,
but these packets go only to routers that need the information. EIGRP also develops neighboring relationships with other routers.

Support for VLSM and CIDR—EIGRP sends the subnet mask information allowing the
network to be divided beyond default subnet masks.

Multiple network layer support—Rather than rely on TCP/IP to send and receive updates,
EIGRP uses Reliable Transport Protocol (RTP) as its own proprietary means of sending
updates.

Independence from routed protocols—EIGRP supports IP, IPX, and AppleTalk. EIGRP has
a modular design that uses protocol-dependant modules (PDMs) to support other routing protocols, so changes to reflect revisions in the other protocols have to be made only to the PDM
and not EIGRP.

Summary
Once you are comfortable with the key features and comparisons of each routing protocol, you
will be able to factor network size, growth potential, Layer 3 addressing, and compatibility into
your selection of the proper routing protocol. If you have read through pages 388–450 of the
CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study, exam #640-801), Second Edition,
it should be very easy to RIP (pun intended) through them again. You can focus on the commands
on a later day. Remember that you have both Day 28 and the curriculum as a reference for today.

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you can configure a local intranet. If your LAN is connected to a WAN. Table 20-1 Network Types Network Type Function Wide-area network (WAN) Connects LANs using serial transmission over a large geographic area to provide remote resources.14_1587131749_DAY20. Clients connect through a secure tunnel to the VPN router at the destination.11—Three main types of VPNs exist: ■ Access VPNs—Allow a client from a home or small office to connect to the main site. ■ Extranet VPNs—Link business partners to an internal network. you create an internetwork. Table 20-1 explains the advanced concepts behind networks that are more than just a LAN. 2. a wireless bridge. e-mail. Storage-area network (SAN) Provides high-performance. and the Internet. You will cover specific WAN service technologies on Day 18. ■ Intranet VPNs—Provide a connection for regional and remote offices for employees. “Choose WAN Services to Meet Customer Requirements.1. Modules 2 and 8 from CCNA 1. Module 8 from CCNA 3.10—A LAN provides connectivity for local devices in the same room or building. . and Modules 1 and 2 from CCNA 4 teach the concepts you need to understand in order to define and design internetworks. 2. Module 2 2.1. you will find storage-area networks (SANs). These partners do not have to be employees of the business.7–2.” CCNA 1. Metropolitan-area network (MAN) Connects LANs in a metropolitan area using private lines. scalable storage for servers over a separate network from the client/server network. you can provide extranet access to this server for Internet users with the proper authentication.12—On a LAN. or optical services.1. and metropolitan-area networks (MANs). Virtual private network (VPN) Provides a private network that exists inside of a public network. fault-tolerant. virtual private networks (VPNs). This intranet provides employees using the LAN browser access to information and applications on a local server. Once you step outside of the LAN.qxd 7/28/06 8:55 AM Page 69 Day 20 Design a Simple Internetwork Using Cisco Technology When you interconnect LANs.1.

To create a static. A segment can represent a physical portion of a network divided by repeaters or a logical portion of a network divided by routers. Millions of cable Internet and digital subscriber line (DSL) subscribers have routers that can implement NAT and PAT. Switches capable of VLANs allow you to use software to logically divide the network into separate broadcast domains. ■ The Layer 2 switch does not allow communication across VLANs without a Layer 3 router. Module 1 1.14_1587131749_DAY20. 1. and each VLAN is its own broadcast domain. DHCP provides a way for any . ■ The switch uses only the MAC address table from a specific VLAN to learn addresses and forward frames for that VLAN. CCNA 4. (Expect more about trunking on Day 14. or you could use the capabilities of the switch to create VLANs. You can use software to control VLAN membership by MAC address or logical address.2—If you have one switch with 24 connected employees.2. “Design an IP Addressing Scheme to Meet Design Requirements. Segments are the OSI Layer 4 protocol data unit (PDU).1. Module 8 8. “Configure a Switch with VLANs and Interswitch Communication. but you can use an RFC 1918 private address range with a LAN and implement network address translation (NAT) and port address translation (PAT) on your router to connect your entire LAN to the Internet with just one outside IP address. ■ The switch is capable of connecting to other switches and sharing VLAN information.1. you could buy two more switches. If you do not want users to move around.” your computer needs a registered IP address to communicate on the Internet. Imagine that these 24 employees belong to three groups and you want to divide the LAN into three broadcast domains. you can map each port on a switch to a VLAN regardless of who connects to that port.7—The term segment holds many meanings in networking. then you have one large broadcast domain.2—If you design a LAN connected to the Internet using NAT and PAT.1.1 and 1. it performs the following actions: ■ The switch maintains a separate MAC address table for each VLAN. To divide this network.1. it would be a great idea to add Dynamic Host Configuration Protocol (DHCP).5—VLANs give you complete control over the logical topology of your network despite the physical arrangement of your switches.3–8. port-centric VLAN.2.1 and 8. CCNA 3.qxd 70 7/28/06 8:55 AM Page 70 31 Days Before Your CCNA Exam CCNA 1.3—As discussed on Day 22.1. Module 8 from CCNA 3 discusses how to segment a network logically with switches.1.2.”) 8. Module 8 8.1–1. When you divide a switch into VLANs. A frame forwarded from VLAN1 on switchA will be seen by VLAN1 on switchB only if the switches are trunked. This dynamic membership VLAN allows users to move around and remain in the same VLAN. you can create a static VLAN.

The DHCPOFFER can include an IP address. and the client can start using the IP address.qxd 7/28/06 8:55 AM Page 71 Day 20 71 host that you connect to the LAN to automatically obtain an IP address from your router using the transport layer User Datagram Protocol (UDP) ports 67 and 68. ■ You must balance the cost of WAN connections with the speed necessary for your WAN to function.3—DHCP offers three types of IP address allocation: ■ Automatic allocation of a permanent address ■ Manual allocation of an address configured by the administrator ■ Dynamic allocation of an address leased for a limited period of time You can configure the DHCP pool to include any range of addresses from one subnet. If the client detects that an IP address is in use on the network. The DHCP server will then send a DHCPACK unicast. DNS server. When the client is done with the IP address. DHCP can lease an IP address to a client from a pool of addresses and provide other configuration information such as a domain name. by default.2—When you design the WAN portion of an internetwork. If the client receives DHCPOFFERs from more than one DHCP server. DHCP replaced the Bootstrap Protocol (BOOTP) as a more advanced means of allocating an IP address. CCNA 4. The client notifies the network that it has accepted a request by broadcasting a DHCPREQUEST with the accepted configuration. A DHCP server will either respond to the broadcast with a unicast DHCPOFFER or forward the request to another DHCP server. BOOTP requires you to configure a static map of IP addresses for each client you add to the network. . 1.14_1587131749_DAY20.2. Configuration parameters you can set for the host in DHCP include the following: ■ Subnet mask ■ Gateway router ■ Domain name ■ Domain name server ■ Windows Internet naming WINS server 1. it will send a DHCPDECLINE and start another request. it will send a DHCPRELEASE.4—To obtain an IP address using DHCP. a client first sends a DHCPDISCOVER broadcast. it will typically accept the first offer it receives. consider the following factors: ■ You will likely purchase your WAN connections from a communications provider for cost and legal reasons.3.2. ■ WANs function at the lower three layers of the OSI model but focus on Layers 1 and 2.1 and 2. A Cisco DCHP server will ping its address pool twice. to check for used IP addresses before sending a DHCPOFFER. Module 2 2. WAN connections are slower than LAN connections but may need to support voice and video as well as data.3. and lease time.

Before turning the page. Step 3 Plan a topology. Summary At the point that you plan to segment LANs and connect them with WAN technologies. Step 6 Evaluate cost. you begin the process to create an entire internetwork. In your notes.14_1587131749_DAY20.qxd 72 7/28/06 8:55 AM Page 72 31 Days Before Your CCNA Exam To design a WAN. consider the following steps: Step 1 Locate LANS. it might help to diagram the DHCP process and key features of VLANs. Your Notes . Step 5 Choose technology. exam #640-801). Step 2 Analyze traffic. Step 4 Plan bandwidth. you will be ready to move on to the even more exciting sections about configuration and troubleshooting. When you study the specific WAN technologies on Day 18. you might like to quickly look at pages 59–68 and 350–354 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Second Edition.

■ Place standard ACLs closest to the destination. Short days like today provide a great opportunity to take a Cisco Academy online practice CCNA test or get a head start on the next day.0.4—Do not look for a relationship between wildcard masks and subnet masks. you use the wildcard mask to specify the range. The wildcard mask 0.168.7 with the wildcard mask 0. Both commands have syntax and parameters that will be covered with examples on Day 10. you use the command access-list in global configuration mode.1. ■ Outbound ACLs do not affect traffic originating from the router. ■ At the end of every ACL. Module 11 11. wildcard masks serve an entirely different function from subnet masks. which is covered in CCNA 2. ■ Do not work with an access list that is applied. 0. A wildcard mask uses binary ANDing to show what part of an IP address should be matched.1.3—Remember the following guidelines for an ACL from Day 25. ■ An ACL should filter specific addresses first and then groups of addresses.0.168. there is an implicit deny.1. . To control traffic with an ACL.0. ■ A router stops checking ACL statements after the first match.15_1587131749_DAY19. “Evaluate Rules for Packet Control”: ■ The way to revise an ACL is to delete and re-create it unless it is a named ACL. ■ A router checks ACL statements in the order in which you create them. you switch to interface mode and use the command ip access-group. To apply the ACL.” When you identify a group of IP addresses in an ACL.qxd 7/28/06 8:55 AM Page 73 Day 19 Develop an Access List to Meet User Specifications Today you review the guidelines for creating an access control list (ACL).1. CCNA 2.255 tells the router that the ACL must match the range 192. As explained on Day 25.0 states that the ACL should match the entire host. To create the ACL.1.0. 11.0.168. Module 11.0 to 192. ■ Place extended ACLs closest to the source. the IP address 192.255.0.0 can also be represented by the term any or host in an ACL. you first create the ACL and then apply the ACL in a direction to a port. “Implement an Access List.1–11. it sends an ICMP implicit deny. ■ You can apply one ACL per protocol per direction per interface.1. ■ When an IP ACL rejects a packet.

you can check the source.6—A router has five virtual ports called VTY lines that you can control with an ACL. but more importantly they also allow you to protect users. Extended ACLs use the number range 100 to 199. 11.2. You should put a standard ACL as close to the destination of the traffic you are filtering as possible because a standard ACL looks only at the source address of a packet. If you have a copy of CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.2. because an extended ACL is able to look at the destination address in a packet. On Day 3.2. look through pages 456–468. and then you create the rules in the list. you can verify that it is present by looking at the configuration or by looking at the specific interface where you applied the ACL.” you will cover the commands and output associated with ACL verification.2.15_1587131749_DAY19. or who is sending the packet. exam #640-801).1.qxd 74 7/28/06 8:55 AM Page 74 31 Days Before Your CCNA Exam 11. and lastly you apply the ACL to an interface.2. and port.3—Remember the following key points about each type of ACL: ■ Standard ACL—This type of ACL uses the number range 1 to 99 and checks only the source address. You should apply the same restrictions to all VTY lines on a router and use only numbered ACLs. ■ Extended ACL—With an extended ACL. Second Edition. 11.4—You should put an extended ACL as close to the source of the traffic you are filtering as possible. The implementation guidelines outlined today prepare you for ACL configuration and troubleshooting on days 10 and 3. Named ACLs can be configured as standard or extended ACLs. 11. “Troubleshoot an Access List.1–11. . ■ Named ACL—Named ACLs do not use a range of numbers because the name is the identifier. Border routers configured with ACLs can act as firewalls and protect internal LANs from attacks that originate from outside your network. destination.5—ACLs allow you to control traffic.5—After you have created and applied an ACL. 11. Summary First you determine the traffic that you want to permit and deny. protocol.

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You connect ISDN with an RJ-45 connector. WANs often provide access over serial interfaces at lower speeds than a LAN. CCNA 1. Frame Relay. and Frame Relay use serial connections and provide speeds ranging from 2400 bps to 1. Now you can view these characteristics with the intent to determine which type of WAN works best for a given situation. RJ-45.10—WANs connect LANs over a large geographically separated area using a modem on a plain old telephone service (POTS) line.6—WAN physical connections include serial. Clients connect through a secure tunnel to the VPN router at the destination. 4. then connect the DB-9 end to the serial port on a computer. Integrated Service Digital Network (ISDN).1. Module 2 2. or E3. and 5 from CCNA 4 provide the content necessary to understand and choose a WAN service. A VPN provides a private network that exists inside of a public network. CCNA 1. Modules 2 and 5 from CCNA 1.2. T3. A LAN can be extended through a public WAN using a virtual private network (VPN). Console RJ-45 to DB-9 Use a rollover cable and connect to the RJ-45 console port on the router.048 Mbps for an E1. RJ-11.1–5. Synchronous Optical Network (SONET).2. Table 18-1 provides a brief description of how to cable WAN services. 3. DSL RJ-11 Connect a DSL router using a standard RJ-11 phone connector and phone line. A BRI U interface includes the NT1. Table 18-1 WAN Physical Connections Connection Physical Type Connectors Cabling Serial 60-pin or smart serial The router connects to a channel service unit/data service unit (CSU/DSU) with a data terminal equipment (DTE) serial cable. . Module 5 5.7 and 2. Cable F-connector Connect a cable modem with a standard coaxial cable and F-connector. Cisco High-Level Data Link Control (HDLC). the router will connect with a BRI S/T interface. and F-connectors.16_1587131749_DAY18. digital subscriber line (DSL). ISDN basic rate interface (BRI) provides two 64 kbps bearer (B) channels and one 16 kbps delta (D) channel. ISDN BRI S/T BRI U If a network termination 1 (NT1) device is needed.1.qxd 7/28/06 8:55 AM Page 77 Day 18 Choose WAN Services to Meet Customer Requirements On Day 24. T1. Point-to-Point Protocol (PPP). E1.54 Mbps for a T1 and 2.” you evaluated the key characteristics of WANs. Module 1 from CCNA 2. “Evaluate Key Characteristics of WANs. and Modules 2.

1–1. Module 2 2.1.1. Frame Relay Circuit switched ISDN 2.1. Link Access Procedure Balanced (LAPB) Packet switched X. PPP. CPU. you are connected to the provider’s nearest exchange. ■ Supervisory frame—This frame controls data frame flow and can request retransmission if an error occurs.1. NVRAM. you will almost always coordinate with a communication service provider such as a local phone company and use routers.25. the phone company provides you a port as the demarcation point. modems. As discussed on Day 24.16_1587131749_DAY18. In your building. and router interfaces are capable of supporting the specific WAN service that you choose.1.1 and 2. or central office (CO).1. When you design a WAN. CCNA 4. A modem can also serve this purpose by modulating and then demodulating the signal in order to pass digital information over an analog line on the public switched telephone network (PSTN). Make sure that the RAM. Routers often act as a gateway from your LAN to a WAN. over the local loop or last mile.21 Synchronous digital up to 64 kbps Table 18-3 WAN Data Link Layer Protocols Type Protocol Point-to-point Cisco HDLC. You commonly use a High-Speed Serial Interface (HSSI) to a CSU/DSU.4—Connections and protocols specific to a WAN operate at OSI Layers 1 and 2.3—As review from Day 24. Table 18-2 WAN Physical Layer Standards Standard Speed EIA/TIA-232 64 kbps EIA/TIA-449/530 Up to 2 Mbps EIA/TIA-612/613 HSSI up to 52 Mbps V. 2.35 48 kbps X. there are three types of HDLC frames: ■ Unnumbered frame—This frame is for line setup messages.qxd 78 7/28/06 8:55 AM Page 78 31 Days Before Your CCNA Exam CCNA 2. Table 18-2 displays the physical layer standards for a WAN. ■ Information frame—This frame holds data. and Table 18-3 displays the data link layer standards for a WAN. Module 1 1. . and communication servers.2—If you have selected a WAN service that uses a communication service provider.4—The most common Layer 2 WAN encapsulation uses the HDLC standard.

Simple. 2. or you can instead choose a switched circuit as one of the following: ■ Circuit-switched in the form of ISDN or POTS ■ Packet-switched in the form of X. Works well for e-mail and small reports. Quick setup using the D channel and high-bandwidth capabilities.25 or Frame Relay ■ Cell-switched as Asynchronous Transfer Mode (ATM) If you choose packet switching and if your bandwidth requirements are low. and 30 B channels and one D channel in other parts of the world. When a virtual circuit needs to exist forever. the provider can allow you to share a physical link with other subscribers. ISDN ISDN modem uses the local loop as a digital connection to the provider. With an SVC. Slower call setup than ISDN. low cost..6—To connect to a WAN.8—Table 18-4 provides a detailed menu of WAN services that you could serve to your client. ■ Frame Relay is an example of a Layer 2 WAN connection-oriented packet-switching system where the route is determined by switches and each frame carries an identifier called a datalink connection identifier (DLCI). as outlined in the following two examples: ■ The Internet is an example of a connectionless packet-switched system where each packet contains full addressing information. continues .2. highly available. You can refer to a temporary virtual circuit as a switched virtual circuit (SVC).S. A connection that shares capacity by switching packets for many nodes is called a packet-switched network (PSN). BRI provides two 64 kbps B channels and one 16 kbps D channel. but for data communication it is possible for many computers to share a connection and take turns requesting and receiving data as packets in short bursts.2.16_1587131749_DAY18.5—The phone system requires continuous connections and is considered a circuit-switched system. you can save money if you request an SVC instead of a PVC. Also serves as a backup for a leased line. Frame Relay switches create a virtual circuit (VC) between communicating hosts that exists only when the frame is being transferred.1. Packetswitched networks can be connectionless or connection-oriented.1. low bandwidth. you can use a dedicated circuit and buy a fractional T1/E1 through T3/E3 or DSL. PRI provides 23 B channels and one 64 kbps D channel in the U.1–2. Table 18-4 WAN Service Menu WAN Service Media and Devices Features Analog dial-up Modem uses copper and connects over the local loop to the PSTN. 2. it is called a permanent virtual circuit (PVC). Intermittent connection over a dedicated circuit. 56 kbps maximum bandwidth.qxd 7/28/06 8:55 AM Page 79 Day 18 79 2.

Offers both private and shared virtual circuits.16_1587131749_DAY18. Mostly replaced by Frame Relay. fixed-capacity links with no latency or jitter. ■ WANs function at the lower three layers of the OSI model but focus on Layers 1 and 2.qxd 80 7/28/06 8:55 AM Page 80 31 Days Before Your CCNA Exam Table 18-4 WAN Service Menu continued WAN Service Media and Devices Features Leased line Router serial port. Frame Relay Typically a leased line. . with private virtual circuits being most common. DSL sends data across the Internet. often capped by the provider. “Design a Simple Internetwork Using Cisco Technology. ■ You must balance the cost of WAN connections with the speed necessary for your WAN to function. ATM Multiple virtual circuits can be provided over a single leased line. works at the network layer.” when you design the WAN portion of an internetwork: ■ You will likely purchase your WAN connections from a communications provider for cost and legal reasons.1 and 2. Allows for bandwidth up to 8.5 kilometers (3. Works more efficiently than X. Cost is based on a fixed bandwidth. Increase in neighborhood users can decrease bandwidth.25 network.2—Recall these key points and steps from Day 20.5 miles).3. Residential shared broadband access providing both television and network connectivity. Uses a higher frequency than the 4 kHz voice channel to send data allowing voice and data to transmit simultaneously. Up to 4 Mbps bandwidth maximum with the capability for a committed information rate (CIR) in a private virtual circuit. very expensive for a network with multiple endpoints. but can also be dial-up to a Frame Relay network.25.25 at the data link layer with frames and virtual circuits such as X. Very fast permanent shared connection that operates using cells rather than frames. A personal firewall and VPN provide security for transmission over the Internet.192 Mbps over many different varieties. Frame Relay is a permanent shared connection. WAN connections are slower than LAN connections but may need to support voice and video as well as data. Standard 53-byte cell provides low latency at a maximum bandwidth above 155 Mbps.25 Dial-up or leased-line connections to an X. DSL DSL modem copper phone lines over the local loop to a DSL Access Multiplexer (DLSAM). so VPN is a common way to secure the connection. Max 48 kbps bandwidth. CSU/DSU connection over copper or optical media.3. X. including symmetric DSL (SDSL) and asymmetric DSL (ADSL). Cable modem Cable modem and coaxial cable connect to the Internet using existing television cabling. 2. Cost is based on the amount of bandwidth used and not a fixed bandwidth. Packet-switched shared service that uses private or shared virtual circuits. often used for point-of-sale machines. Speeds up to 40 Mbps. The local loop must be less than 5. Point-to-point permanent dedicated connection.

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As mentioned on Day 20, you should consider the following steps to design a WAN:
Step 1

Locate LANS.

Step 2

Analyze traffic.

Step 3

Plan a topology.

Step 4

Plan bandwidth.

Step 5

Choose technology.

Step 6

Evaluate cost.

2.3.3—The most common WAN design connects a main point to branch networks in a star topol-

ogy. A partial mesh topology may also work well to provide better reliability. You would commonly use ISDN or DSL to connect a small office or home office (SOHO). You could choose Frame
Relay or leased lines to connect larger branch offices to a WAN. A short leased line that connects
each office to a Frame Relay network would cost much less than connecting each branch with long
leased lines. If you need a high-bandwidth network with low latency, consider leased lines, ATM,
or Frame Relay with a CIR or quality of service (QoS) mechanism. Remember that a shared service such as ATM or Frame Relay will cost less than a leased line.
2.3.4 and 2.3.5—If you had to connect 900 office branches, a flat WAN topology would not pro-

vide very good service. The three-layer hierarchical design provides an excellent structure for
WAN design. If you are designing for a business, you can parallel the region, area, and branch
with the core, distribution, and access layer design. The three-layer design helps you to better
implement, scale, manage, and troubleshoot a WAN. An example design you could implement
would be to connect branches with Frame Relay to regions that use an ATM backbone to connect
to the main office. Use the structure of the three-layer model to help define bandwidth and organizational aspects of a WAN. You can always adjust the layers to fit your specific topology and focus
on only two layers for a network that best fits that design.
2.3.6—How your WAN connects to the Internet is a key security factor in your design. If you

connect to the Internet at an office only, then you have only one connection to secure, but all
Internet traffic must pass over your WAN connections to branch offices. If each branch connects to
the Internet, you have less WAN traffic but more vulnerable points on your WAN. Some companies tunnel WAN traffic only over Internet connections, which saves connectivity costs and enables
more spending on added security.

CCNA 4, Module 3
3.1.1–3.1.4—WAN serial communication requires that frames are sent one bit at a time over the

wire. Serial communication standards include RS-232-E, V.35, and HSSI. Multiple devices and
users can connect with a single serial connection using time division multiplexing (TDM). Each
transmitting device has a time slot on the serial connection that it can use to transmit. In the United
States, you are responsible for maintaining the CSU/DSU at the demarcation point. A router that
you connect to the CSU/DSU is considered the customer premises equipment (CPE). In other
countries, the network terminating unit (NTU) is managed by the communications provider.

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Typically, your CPE router is considered the DTE, and the communication provider has the DCE
equipment and provides clocking.
3.1.5—Cisco HDLC encapsulation, as mentioned previously in the section “CCNA 4, Module 2”
under 2.1.4, is the default Layer 2 encapsulation for a serial link and defines an unnumbered,
information, and supervisory frame. Cisco HDLC uses synchronous serial transmission and supports multiple protocols using a proprietary type field as a Layer 3 protocol field.
3.2.1–3.2.6—PPP is a layered protocol that provides transmission for multiple network layer pro-

tocols and tests connectivity using the data link layer. You can configure PPP to operate on asynchronous serial, synchronous serial, HSSI, and ISDN. PPP uses the Link Control Protocol (LCP)
to establish the link and the Network Control Protocol (NCP) to configure the Layer 3 protocols.
LCP includes the following options:

Authentication—You can require the device making the call to authenticate using the clear
text Password Authentication Protocol (PAP) or the more secure and encrypted Challenge
Handshake Authentication Protocol (CHAP). PAP authenticates only once, while CHAP frequently rechecks the authentication.

Compression—This option can increase throughput on the link, and the receiving device
decompresses the frames. Stacker and Predictor are two types of compression available on a
Cisco router.

Error detection—Quality and Magic Number options can help keep the link reliable.

Multilink—This option allows for load balancing over multiple PPP-configured router interfaces. This feature is available with Cisco IOS Software Release 11.1 and later.

PPP callback—This security feature allows the client to first call and then request the router
to call back with a specific configuration. This feature is available with Cisco IOS Software
Release 11.1 and later.

NCP uses a separate protocol to control each network layer protocol. An example would be that,
for IP, NCP uses IP Control Protocol (IPCP). A PPP frame consists of a flag field, an address field,
a control field, a protocol field, a data field, and a frame check sequence (FCS) field. Table 18-5
describes each of the phases of the PPP session establishment.
Table 18-5

PPP Session Establishment

Phase

Description

Link establishment phase

Each device sends LCP frames, and they negotiate LCP options; then
LCP opens the connection with a configuration acknowledgment frame.

Authentication phase (optional)

The established link can authenticate using PAP or CHAP and also check
link quality.

Network layer protocol phase

PPP devices send NCP packets to configure network layer protocols and
allow Layer 3 transmission.

Inactivity timers, user intervention, and NCP or LCP frames can close a PPP link.

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CCNA 4, Module 4
4.1.1–4.1.3—Local carriers use ISDN to provide a digital connection on the local loop for a subscriber that allows you to exceed the 56 kbps bandwidth barrier of an analog connection. ISDN
BRI has two B channels at 64 kbps for data and one D channel at 16 kbps for call setup. ISDN can
use PPP encapsulation. The three categories for ISDN protocols are as follows:

E Series—Telephone network standards

I Series—ISDN concepts and terminology

Q Series—How switching and call setup (signaling) function, including Q.921 link access
procedure on the D channel (LAPD) and the Q.931 ISDN network layer

ISDN uses out-of-band signaling, which means that the D channel handles call setup using LAPD
outside of the data paths in the B channels. As described in Table 18-4, ISDN can provide 2 B
channels and 1 D channel with BRI or 23 B channels and 1 D channel with PRI. Outside of
America and Japan, PRI offers 30 B channels. ISDN PRI provides the same service as a T1/E1
connection. Table 18-6 outlines the fields of an ISDN frame.
Table 18-6

ISDN Frame Fields

Field

Description

Flag

Beginning of the frame.

Address Contains the following information:
Service access point identifier (SAPI)—Identifies the Layer 3 portal
Command and response (C/R) bit—Identifies whether the frame has a command or response bit
Extended addressing (EA) bits—Identifies if the address is 1 byte or 2 bytes
Terminal endpoint identifier (TEI)—Unique equipment identifier
Control

Similar to HDLC.

Data

Encapsulated data for upper layers.

FCS

Frame Check Sequence allows a check for damaged frames using a cyclic redundancy check
(CRC).

Flag

End of the frame.

4.1.4—To establish a BRI or PRI call, the D channel first sends the called number to the ISDN
switch. The local switch uses the Signaling System 7 (SS7) signaling to set up a path. The remote
switch signals the destination over the D channel. The destination NT1 device sends the remote
ISDN switch a call-connect message, and the remote ISDN switch uses SS7 to send a call-connect
to the local switch. The local switch connects one B channel for end-to-end communication. The
other B channel is available for a later connection. In essence, ISDN switches use the D channel
and SS7 signaling to establish data links on the B channel.
4.1.5—The ISDN reference points on a chart resemble alphabet soup. Either you have a terminal
equipment 1 (TE1) device with a native ISDN interface or a terminal equipment 2 (TE2) device

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that requires a terminal adapter (TA) to connect to ISDN. The following two written examples and
Figure 18-1 depict each of the ISDN reference point locations based on your TE1 or TE2:

You have a TE1 that is a native ISDN interface that connects at the S reference to the customer switching network termination type 2 (NT2). The NT2 connects at the T reference to
the network termination type 1 (NT1), and the NT1 connects at the U reference to the local
loop.

You have a TE2 that is nonnative ISDN, so you first connect at the R reference to the TA and
then to the NT2. The NT2 connects at the T reference to the NT1, and the NT1 connects at
the U reference to the local loop.

S and T references can be similar, so you may sometimes see an S/T interface.
Figure 18-1

ISDN Reference Points

S

NT2

TE1

TE2

Existing
Terminal

T

NT1

U

Service
Provider Network

Local
Loop

R

TA

Terminal
Adapter

4.1.6 and 4.1.7—When determining the appropriate ISDN interface on a router, remember the

following:

Look at the back of the router and determine if there is a BRI interface or BRI WAN interface
card (WIC).

Determine whether or not you have to provide the NT1 device to terminate the local loop to
the CO. In the United States, you will have to provide the NT1; in other countries, the
provider supplies the NT1.

If the router has a U interface, the NT1 is built in, but if the router has an S/T interface, it
needs an external connector.

If the router has a BRI interface and does not have an NT1 built in, it will need to connect to
an NT1.

If the router has only serial interfaces, it is a TE2 and will need a TA to connect to the NT1.

To connect to the provider, make sure that you have the switch type and the service profile identifiers (SPIDs) for the provider. SPIDs are used in North America and Japan to identify the B channel. SPIDs resemble phone numbers.

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CCNA 4, Module 5
5.1.1—Frame Relay is a packet-switched, connection-oriented, data link layer WAN technology.

Frame Relay uses a subset of HDLC called Link Access Procedure for Frame Relay (LAPF) for
encapsulation. Once the frame is forwarded from the DTE router to a DCE Frame Relay switch,
the network of Frame Relay switches moves the data to its destination. Typically, you will subscribe to a network of trunked Frame Relay switches owned by a public carrier.
5.1.2—The following process would allow you to connect LAN1 to LAN2 across town using
Frame Relay:

1. You call the phone company and connect your LAN1 router to their nearest Frame Relay
switch. Your LAN1 router will have a unique DLCI that identifies it on the Frame Relay
switch network.
2. You then connect the LAN2 router to a nearby Frame Relay switch on the same phone company network. LAN2 will also have a DLCI that identifies it on the Frame Relay network.
3. The phone company uses its Frame Relay switches to then establish a packet-switched PVC
across town for your two LANs.
4. The routers on LAN1 and LAN2 operate as Frame Relay access devices (FRADs).
5.1.3—Frame Relay receives a packet from a Layer 3 protocol and encapsulates it as a Layer 2
frame to transfer over the Frame Relay network. If a frame does not match its FCS upon delivery,
the frame is simply dropped and error control is left for the upper layers.
5.1.4—Your initial connection to a Frame Relay network will commonly be over a leased line.
The provider determines the bandwidth of the leased line and can also provide a CIR for your
PVC on the Frame Relay network. It is possible for your network to use more than your CIR on
the Frame Relay network, but every allowed frame that is over the CIR will be marked as discard
eligible (DE) with a 1 in the DE bit of the address field. These DE frames will be dropped first if
congestion occurs. Frame Relay switches avoid congestion by using an explicit congestion notification (ECN) bit in the frame address field. The Frame Relay switch will set the Forward ECN
(FECN) bit and Backward ECN (BECN) bit on received and sent frames to notify the DTEs to
reduce flow.
5.1.5—Routers that you connect to a Frame Relay network receive a DLCI to identify the virtual
circuit (VC). You can configure a physical interface to support multiple VCs and multiple DLCIs.
Remember that the DLCI for each VC must be associated with the network address of its remote
router. The DLCI associations or mappings can be configured using map commands or automatically with inverse ARP.
5.1.6—The 10-bit DLCI field in a Frame Relay frame permits VC identifiers 0 through 1023.
Some of these identifiers are reserved for link management identifiers (LMIs). LMIs allow DTEs
to exchange information and dynamically learn information about the status of the network. Cisco
routers support Cisco, ANSI, and Q933a-type LMIs. LMI 0 is used by ANSI and q933a, and LMI
1023 is used by Cisco. LMI messages are slightly different from the regular LAPF frames. LMI
frames include information about the status of a DLCI.

you will at some point be required to defend your decision. The connected router can use the inverse ARP replies to populate its DLCI map table.qxd 86 7/28/06 8:55 AM Page 86 31 Days Before Your CCNA Exam 5. 520–532. Second Edition. Your Notes . Summary Whether you decide to use dial-up. exam #640-801). ISDN. The router can map VCs to network layer addresses by sending an inverse ARP message to each VC and including its own network layer address. The network responds with details of every VC configured on the link. You will probably have to talk about cost. Frame Relay.16_1587131749_DAY18. and 548–564 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. logical. Your well-rounded knowledge of the physical. 488–502. or two cans and a string. and design aspects of each WAN service will serve you well. A router will send inverse ARP messages for each network layer protocol. You can review everything but WAN costs in a more flashy format by reading pages 174–196. but that changes regularly and is not covered in the CCNA.7—A router that is connected to a Frame Relay network will send LMI status inquiry mes- sages to the network.1.

and Gateway Addresses on Routers and Hosts Day 15: Configure a Router for Additional Administrative Functionality Day 14: Configure a Switch with VLANs and Interswitch Communication Day 13: Implement a LAN Day 12: Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives) Day 11: Perform an Initial Configuration on a Router and Perform an Initial Configuration on a Switch (Two Objectives) Day 10: Implement Access Lists Day 9: Implement Simple WAN Protocols . Subnet Masks.17_1587131749_Pt3.qxd 7/28/06 8:55 AM Page 87 Part III 17–9 Days Before the Exam— Implementation and Operation Day 17: Configure Routing Protocols Given User Requirements Day 16: Configure IP Addresses.

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1. Modules 1. as well as the syntax and examples. 6.0 255. Consider the information provided here a primer for hands-on review in the lab or with a simulator.255. CCNA 2. ■ Use protocols that will select the best path.1. Module 1 1. Today.255.1.1. Routing protocol configurations will only work once you have configured the interfaces on a router.2 . 2. Do not practice on your gateway router at work. you should keep the following points in mind as you configure the routers: ■ Maintain consistent addressing that represents your network topologies. These chapters help you to recognize and remember the commands. on real routers at your academy. the e-labs.0 192. On the CCNA exam.168. You will cover interface configuration on a Day 16. and Gateway Addresses on Routers and Hosts. you review the syntax for a routing protocol configuration and see examples of how the commands should look in the command-line interface (CLI).3—The syntax for a static route follows: ip route destination-network subnet-mask {outgoing-interface | next-hop-address} Example 17-1 Configuring a Static Route Router(config)#ip route 192. and 3 from CCNA 3 discuss routing protocol configurations. To master these commands.qxd 7/28/06 8:55 AM Page 89 Day 17 Configure Routing Protocols Given User Requirements The configuration and troubleshooting CCNA exam objectives that introduce configuration commands in this book will provide a quick definition for a set of commands. CCNA 2. or even better. you should also practice with a simulator.” Most routing configurations start in global configuration mode. Module 6 6. “Configure IP Addresses. The days that cover configuration and troubleshooting will help you to quickly orient your knowledge while reading snippets of configuration information.168. ■ Use dynamic routing for ease of configuration and static routes for specific routing needs. and 7 from CCNA 2 and Modules 1. Subnet Masks.18_1587131749_DAY17.3—When you have connected all the cables and devices that constitute a WAN. It is very important that you become accustomed to recognizing the command mode from the prompt. you will encounter portions of a routing configuration and partial sets of commands.

The ip classless command is on by default on most routers.0.1.5—The commands shown in Example 17-3 allow you to check your static and default routes.0 s0 6.2.2.0 0.1. Module 7 7.168.0 7.0.0.18_1587131749_DAY17.168.1. Example 17-5 The ip classless Command Router(config)#ip classless 7.2.2.0 0.0.0 {outgoing-interface | next-hop-address} Example 17-2 Configuring a Default Route Router(config)#ip route 0.2—The syntax to enable and configure Routing Information Protocol (RIP) is as follows: router rip network directly-connected-network Example 17-4 Configuring RIP Router(config)#router rip Router(config-router)#network 192. Example 17-3 Verifying Static and Default Routes Router#show running-config Router#show ip route CCNA 2.4—The syntax for a default route follows: ip route 0.0.0.3—The ip classless command shown in Example 17-5 allows a router to ignore network class boundaries.0 Router(config-router)#network 192.7—The following command syntax prevents routing updates from transmitting on an interface: router rip passive-interface interface Example 17-6 The passive-interface Command Router(config)#router rip Router(config-router)#passive-interface fa0/0 .0.qxd 90 7/28/06 8:55 AM Page 90 31 Days Before Your CCNA Exam 6.0.

The following command increases the AD of a static route to 130 so that a dynamic route with an AD of 120 will take priority in the routing table. The following com- mand sets the number of paths: router rip maximum-paths {0-6} Example 17-7 Setting Load Balancing Maximum Paths Router(config)#router rip Router(config-router)#maximum-paths 3 To tell a router to load balance on a per-packet basis rather than a per-destination basis.1. use the following syntax: interface interface no ip route-cache Example 17-8 Setting an Interface to Route on a Per-Packet Basis Router(config)#interface s0/0 Router(config-if)#no ip route-cache 7.5—The following commands allow you to enable and configure Interior Gateway Routing Protocol (IGRP): router igrp autonomous-system-number network directly-connected-network .0 255.qxd 7/28/06 8:55 AM Page 91 Day 17 91 7. as shown in Example 17-10.255. Example 17-9 Configuring a Static Route with an Administrative Distance Router(config)#ip route 192.2 7.1.3.168.2.0 192.168.168.9—RIP can load balance traffic over up to six network paths. You add the administrative distance option to the end of your static route configuration.255.2.18_1587131749_DAY17.168.255.2. Example 17-10 Removing a Static Route Router(config)#no ip route 192.8 and 7.10—You can dictate the priority of a route using the administrative distance (AD).255.1.0 192.1.0 255.2 130 You can also remove a static route by adding a no in front of the command.

you need to configure the interface with the proper subnet mask in order for routing with VLSM to work properly.7—IGRP has an administrative distance of 100 and will take priority over RIP entries in a routing table.4 and 1. If you have a router with both protocols configured. Module 1 1.3.2. you can configure a routing protocol such as RIP version 2 that supports VLSM. you can view information about the protocols and verify IGRP configuration with the commands shown in Example 17-12.168.6 and 7. 1.252 Once you have configured all the interfaces with the proper subnet masks.3. Example 17-12 Viewing Configured Protocols Router#show ip protocols Router#show ip route Router#show running-config Router#show interface CCNA 3.255.2 255. The configuration of the correct mask allows the routing protocol to advertise the right mask with each network.1.2.qxd 92 7/28/06 8:55 AM Page 92 31 Days Before Your CCNA Exam Example 17-11 Configuring IGRP Router(config)#router igrp 101 Router(config-router)#network 192.5—RIP version 2 configuration syntax is as follows: router rip version 2 network directly-connected-network .0.1.0 7. You would use the following interface configuration syntax on a serial interface with a point-to-point connection that requires only a two-host network: ip address ip-address subnet-mask Example 17-13 Configuring an Interface with VLSM Router(config)#interface serial 0 Router(config-if)#ip address 192.6—Although variable-length subnet mask (VLSM) support is a component of a routing proto- col.18_1587131749_DAY17.168.0 Router(config-router)#network 192.168.2.255.

0 0. CCNA 3.0.1—The following is the command syntax for Open Shortest Path First (OSPF): router ospf process-id network network-address wildcard-mask area area-id Example 17-15 Configuring OSPF Router(config)#router ospf 1 Router(config-router)#network 192.0.168.255 All OSPF routers have a default priority of zero.2—OSPF uses the highest local IP address as its router ID unless a loopback interface exists. you can set the OSPF priority with the following configuration: ip ospf priority {0-255} Example 17-17 Configuring the OSPF Router Priority Router(config)#interface serial 0 Router(config-if)#ip ospf priority 40 .255.0 0. The loopback interface should be configured with a host mask.255 area 0 2.255. Loopbacks are used to ensure that a router always has an active interface.0.1.168. you can verify RIP version 2 configuration with the commands listed previously in Example 17-12.255 area 0 Router(config-router)#network 192. which is a 32-bit mask. The following command configures the loopback interface to guarantee OSPF reliability: ip address ip-address subnet-mask Example 17-16 Configuring the Loopback Interface with a Host Mask Router(config)#interface loopback 0 Router(config-if)#ip address 192.0.168. in which case the highest loopback IP address will become the router ID. Module 2 2. To control the designated router election process.1.9 255.3.2.168.3.18_1587131749_DAY17.qxd 7/28/06 8:55 AM Page 93 Day 17 93 Example 17-14 Configuring RIP Version 2 Router(config)#router rip Router(config-router)#version 2 Router(config-router)#network 192. and the highest priority wins.0 Just as with RIP and IGRP.0.

You can override this calculation by manually setting the cost.qxd 94 7/28/06 8:55 AM Page 94 31 Days Before Your CCNA Exam You can verify OSPF priority configuration with the following command: show ip ospf priority interface interface Example 17-18 Verifying the OSPF Router Priority Configuration Router(config)#show ip ospf interface serial 0 2.3—You can control the priority of an OSPF route by adjusting the bandwidth and cost.535} Example 17-19 Configuring the Bandwidth of an Interface Router(config)#interface serial 0 Router(config-if)#bandwidth 64 Example 17-20 Configuring the OSPF Cost for an Interface Router(config)#interface serial 0 Router(config-if)#ip ospf cost 1 2.3. OSPF automatically calculates the interface cost based on bandwidth.3. You can control the priority of the link on your network with the following commands: bandwidth bandwidth ip ospf cost {1-65.18_1587131749_DAY17. Altering the bandwidth alters the cost.4—The following commands will configure simple OSPF authentication: ip ospf authentication-key password area area-number authentication Example 17-21 Configuring Simple OSPF Authentication Router(config)#interface serial 0 Router(config-if)#ip ospf authentication-key cisco Router(config-if)#exit Router(config)#router ospf 1 Router(dhcp-config)#area 0 authentication The following commands configure OSPF authentication with MD5 encryption: ip ospf message-digest-key key-id md5 key area area-number authentication message-digest .

These values work fine.0.18_1587131749_DAY17.0.0.6—To add a default route and then propagate that route with OSPF. but if you would like. The default values are 10 seconds for a hello and 40 seconds for a dead interval timer. and debug commands: show ip protocol show ip route show ip ospf interface show ip ospf show ip ospf neighbor detail show ip ospf database clear ip route * clear ip route next-hop-address debug ip ospf events debug ip ospf adj .0. use the following commands: ip route 0.3.0.3.7–2.0 0. clear.0.0 {interface |next-hop-address} default-information originate Example 17-24 Propagating a Default Route with OSPF Router(config)#ip route 0.0.3.3.0 serial 0 Router(config)#router ospf 1 Router(config-router)#default-information originate 2.5—You must have the same hello and dead timer intervals in OSPF in order for your routers to exchange information. you can change them with the following commands: ip ospf hello-interval seconds ip ospf dead-interval seconds Example 17-23 Configuring OSPF Hello and Dead Intervals Router(config)#interface serial 0 Router(config-if)#ip ospf hello-interval 5 Router(config-if)#ip ospf hello-interval 20 2.0.8—You can check OSPF operation and configuration using the following show.0 0.qxd 7/28/06 8:55 AM Page 95 Day 17 95 Example 17-22 Configuring OSPF Authentication with MD5 Encryption Router(config)#interface serial 0 Router(config-if)#ip ospf message-digest-key 1 md5 cisco Router(config-if)#exit Router(config)#router ospf 1 Router(dhcp-config)#area 0 authentication message-digest 2.

0 Router(config-router)#network 192.1.255.0 .168.1—The following commands enable Enhanced Interior Gateway Routing Protocol (EIGRP) and configure bandwidth and logging: router eigrp autonomous-system-number network network-number eigrp log-neighbor-changes Example 17-25 Configuring EIGRP and Logging Router(config)#router eigrp 10 Router(config-router)#network 192.0 Router(config-router)#eigrp log-neighbor-changes The following command configures EIGRP bandwidth: bandwidth bandwidth Example 17-26 Configuring EIGRP Bandwidth Router(config)#interface serial 0 Router(config-if)#bandwidth 56 3.168.0.18_1587131749_DAY17.2.2. you can use the following command: no auto-summary Example 17-27 Turning Off EIGRP Route Summarization Router(config)#router eigrp 10 Router(config-router)#no auto-summary You can also manually configure a summary address with the following command: ip summary-address eigrp as-number ip-address mask administrative-distance Example 17-28 Manually Configuring EIGRP Route Summarization Router(config)#interface serial 0 Router(config-if)#ip summary-address eigrp 10 172. Module 3 3.2—If you want to turn off route summary in EIGRP for subnets that are not continuous.2.16.qxd 96 7/28/06 8:55 AM Page 96 31 Days Before Your CCNA Exam CCNA 3.0 255.0.

IGRP.qxd 7/28/06 8:55 AM Page 97 Day 17 97 3.2.7—As discussed on Day 28.4–3. Second Edition. . but sitting at a router or simulator will internalize the steps and commands. Summary The configurations for RIP.18_1587131749_DAY17.” from concepts to configuration.2. “Evaluate the Characteristics of Routing Protocols. exam #640-801). can give you a great overview of everything “routy. and EIGRP should at this point be easy to recognize and use if you intend to be CCNA test ready.” EIGRP uses the diffusing update algorithm (DUAL) to maintain a neighbor table and topology table of available routes. The successor route is considered the best route and is added to the topology table as well as the routing table. OSPF. Skimming through these examples will help jog your memory.2. Pages 388–454 from the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.3—The following show commands allow you to verify EIGRP: show ip eigrp neighbors show ip eigrp interfaces show ip eigrp topology 3. A backup route called the feasible successor is kept in the topology table.

qxd 98 7/28/06 8:55 AM 31 Days Before Your CCNA Exam Your Notes Page 98 .18_1587131749_DAY17.

subnetting. CCNA 2. Remember to apply the conventions in IP addressing covered on those days when you configure the interfaces on a router and your network hosts.1—To use the CLI on a router. you can use Cisco IOS software. Your knowledge of IP addressing.7—On Day 27.1. but the masks and interface addresses you choose for your routers are pillars in your logical network design.” and Day 22. routing protocols.1.” you reviewed the proper dotted decimal format for an IP address and subnet masks. Module 1 1. and Gateway Addresses on Routers and Hosts A minute to configure.19_1587131749_DAY16.2. you review the syntax for interfacerelated configuration commands and see examples of how the commands should look in the command-line interface (CLI). You need to configure IP addresses and subnet masks on both hosts and routers to complete a network. CCNA 1. Module 3 3. CCNA 1. To configure an IP on a router interface. You can assign an address to a host using the operating system or configure the host to obtain the IP address automatically. Module 9 9.2.1–9. a lifetime to address. and variable-length subnet masks (VLSMs) converge when you decide to configure an IP address and mask on your router interface. Consider the information provided here a primer for hands-on review in the lab or with a simulator. Module 3 from CCNA 2. Today. Modules 1 and 9 from CCNA 1. “Design an IP Addressing Scheme to Meet Design Requirements. “Evaluate the TCP/IP Communication Process and Its Associated Protocols. Figure 16-1 and Table 16-1 provide examples of the modes available to you for router configuration.qxd 7/28/06 8:56 AM Page 99 Day 16 Configure IP Addresses. . Subnet Masks. and Modules 1 and 2 from CCNA 3 outline the various interface configuration commands. you must know the hierarchy of configuration modes. The configuration is simple and short.6—Routers and hosts use TCP/IP to communicate across a network.

interface type slot/port ip address ip-address netmask clock rate clock-rate no shutdown .1. You use the clock rate command only if you are configuring a data communications equipment (DCE) interface. Example 16-1 Entering Interface Configuration Mode for Serial 0 Router>enable Router#configure terminal Router(config)#interface serial 0 Router(config-if)# 3.qxd 100 7/28/06 8:56 AM Page 100 31 Days Before Your CCNA Exam Figure 16-1 Router Modes Router> • User EXEC mode • Privileged EXEC mode Router# • Global configuration mode • Specific configuration modes Router (config) # Table 16-1 Configuration Modes and Prompts Configuration Mode Prompt Interface Router(config-if)# Subinterface Router(config-subif)# Controller Router(config-controller)# Map-list Router(config-map-list)# Map-class Router(config-map-class)# Line Router(config-line)# Router Router(config-router)# IPX-router Router(config-ipx-router)# Route-map Router(config-route-map)# Example 16-1 shows the commands you would use to enter interface configuration mode.19_1587131749_DAY16.5—You use the following command syntax to configure a serial interface.

6—You can use the no form of a command to remove the configuration.255.1 255.0 Router(config-if)#no shutdown 3.3—Keeping good standardized documentation of your router configurations is impera- tive for an organized network.0 Router(config-if)#clock rate 56000 Router(config-if)#no shutdown 3.1.255.1 255.255.7—You use the following command set to configure an Ethernet interface: interface type slot/port ip address ip-address netmask no shutdown Example 16-4 Configuring an Ethernet Interface Router(config)#interface fastethernet 0/0 Router(config-if)#ip address 172.16.1.255.16.1.1–3.255.qxd 7/28/06 8:56 AM Page 101 Day 16 Example 16-2 101 Configuring a Serial Interface Router(config)#interface serial 0/0 Router(config-if)#ip address 172.19_1587131749_DAY16. Example 16-3 would remove the IP address and clock rate from the interface configured in Example 16-2 and shut down the interface. The following commands allow you to add an interface description: interface type slot/port description interface-description .1. Example 16-3 Removing Previously Entered Configurations Router(config)#interface serial 0/0 Router(config-if)#no ip address 172.2. A good start is to add a description to each interface so that you or anyone configuring the router can quickly identify the purpose and location of the interface.2. and save the configuration to nonvolatile RAM (NVRAM) by using the following commands in global configuration mode: show running-config copy running-config startup-config 3.255.0 Router(config-if)#no clock rate 56000 Router(config-if)#shutdown You can always check your entire configuration. including all interface configurations.16.1 255.2.

0.19_1587131749_DAY16.255.6—As discussed on Day 17.0. CCNA 3.240 CCNA 3. Example 16-6 Configuring a Serial Interface for a Point-to-Point Link Router(config)#interface serial 0 Router(config-if)#ip address 172. Floor 11 When you have completed an interface configuration.3. Also remember to copy your running configuration to NVRAM in order to save the changes you have made.255 . “Configure Routing Protocols Given User Requirements. Module 2 2. Open Shortest Path First (OSPF) cannot function reliably with- out an interface that is always active. Example 16-8 Configuring the Loopback Interface with a Host Mask Router(config)#interface loopback 0 Router(config-if)#ip address 192.9 255.255. You might use the configurations in Examples 16-6 and 16-7 if you were running RIP version 2 and only needed two IP addresses for a serial point-to-point link and a 12-host network for a LAN.255. you can change modes back to privileged exec quickly using Ctrl-Z.1.255. or by entering the end command. Module 1 1.168.0.16. Make sure that your router is running a routing protocol that supports VLSM.16.qxd 102 7/28/06 8:56 AM Page 102 31 Days Before Your CCNA Exam Example 16-5 Configuring a Description for an Ethernet Interface Router(config)#interface fastethernet 0 Router(config-if)#description Accounting LAN.252 Example 16-7 Configuring an Ethernet Interface for a 12-Host LAN Router(config)#interface ethernet 0 Router(config-if)#ip address 172.” you can configure routers with VLSM in networks to more efficiently use IP addresses.255.17 255.2—As mentioned on Day 17. If you have more than one loopback device configured. You configure the loopback interface on an OSPF router to ensure that you have an always-active interface.255.2 255. OSPF will use the highest loopback IP address as the router ID.

While you are practicing commands and taking curriculum practice exams. You will find questions concerning command modes and interface configuration mixed in with a few other commands on pages 198–238 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. exam #640-801). be sure to pay attention to the command mode for each command that you encounter.19_1587131749_DAY16. Second Edition. .qxd 7/28/06 8:56 AM Page 103 Day 16 103 Summary Routing protocols function properly only if interfaces are configured properly.

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2—The following command allows you to set a router hostname: hostname hostname Example 15-1 Configuring a Router Hostname Router(config)#hostname Portland Portland(config)# 3. as follows: password password login .3—You can restrict console access to a router with the following command: password password login Example 15-2 Setting the Console Password Router(config)#line console 0 Router(config-line)#password cisco Router(config-line)#login If you intend to access a router using Telnet.1. Module 3 3. you will need to set the virtual terminal password.20_1587131749_DAY15. CCNA 2. and port address translation (PAT) configurations. Today.qxd 7/28/06 8:56 AM Page 105 Day 15 Configure a Router for Additional Administrative Functionality Although Layer 3 path selection is the key function of a router. and PAT configuration commands and see examples of how the commands should look in the command-line interface (CLI).1. you review the syntax for password. The CCNA exam covers password configuration as well as Dynamic Host Configuration Protocol (DHCP). network address translation (NAT). DHCP. there are many other parameters that you can configure. NAT. Consider today’s information a primer for hands-on review in the lab or with a simulator. Module 3 from CCNA 2 and Modules 1 and 6 from CCNA 4 provide additional configurations for your router.

use the following command: service password-encryption Example 15-6 Encrypting all Unencrypted Passwords Router(config)#service password-encryption 3. you must use the following command: enable password password Example 15-4 Setting the Password for Privileged EXEC Router(config)#enable password class To encrypt and set the privileged EXEC password.1. access.20_1587131749_DAY15. set- tings.4—The following show commands provide you with information about the files. use the following command: enable secret password Example 15-5 Setting the Console Password Router(config)#enable secret class To encrypt all unencrypted passwords.qxd 106 7/28/06 8:56 AM Page 106 31 Days Before Your CCNA Exam Example 15-3 Setting the VTY Password Router(config)#line vty 0 4 Router(config-line)#password cisco Router(config-line)#login To restrict access to privileged EXEC mode. and configuration of a router: ■ show interfaces—Displays interface information ■ show controllers serial—Displays interface hardware information ■ show clock—Displays router time settings ■ show hosts—Displays hostname and address cache ■ show users—Displays connected users ■ show history—Displays previously entered commands ■ show flash—Displays flash memory and Cisco IOS file information ■ show version—Displays information about the loaded operating system as well as hardware information .

1.33 192.2.168. you have to add a static NAT entry and then label the outside and inside interfaces using the following commands: ip nat inside source static local-IP-address global-IP-address ip nat outside ip nat inside .20_1587131749_DAY15. Module 1 1.6 and 3.2.5—You use the following commands to display a message before a user logs in to the router: banner motd delimiting-character banner-message delimiting-character Example 15-7 Setting a Login Banner Router(config)#banner motd # Authorized Access Only # 3.2. To configure static NAT.1.2. you can use the following command: ip host {name} {IP-address} Example 15-8 Associating a Name with an IP Address Router(config)#ip host boise 192. Example 15-9 Associating a Name with an IP Address Router#ping boise CCNA 4.qxd 7/28/06 8:56 AM Page 107 Day 15 ■ show arp—Displays the Address Resolution Protocol (ARP) table ■ show protocols—Displays information about presently configured Layer 3 protocols ■ show startup-config—Displays the configuration saved in the NVRAM ■ show running-config—Displays the running configuration in RAM 107 3.2.168.1 You can test your configuration by using the ping command with the new hostnames on the router that you have configured.4 and 3.7—To associate a name with one or multiple IP addresses on a router.4—Static NAT is designed to allow one-to-one mapping of local and global addresses. as shown in Example 15-9.

0.200.224 Router(config)#access-list 1 permit 192.0 0.165.20_1587131749_DAY15.255 Once you have defined a pool of outside addresses and a range of inside addresses with an access list.255.200.235 netmask 255.168.1. you set NAT to use the two groups for translation with the following commands: ip nat inside source list access-list-number pool pool-name ip nat outside ip nat inside Example 15-12 Configuring Dynamic NAT Router(config)#ip nat inside source list 1 pool isp-pool Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside If you configure NAT with overload.225 209.0.168.226 Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside To configure dynamic NAT.165. you define a pool of global addresses and then use an access list to define the range of inside addresses that are eligible to be converted with the following commands: ip nat pool pool-name start-IP-address end-IP-address netmask netmask access-list access-list-number permit inside-network wildcard-mask Example 15-11 Defining Inside and Outside Addresses for Dynamic NAT Configuration Router(config)#ip nat pool isp-pool 209. You can configure overload to translate many addresses to just one outside IP address that is assigned to an interface using the following commands: access-list access-list-number permit inside-network wildcard-mask ip nat inside source list access-list-number interface interface overload ip nat outside ip nat inside .200.255.165.1. you have enabled PAT.5 209.qxd 108 7/28/06 8:56 AM Page 108 31 Days Before Your CCNA Exam Example 15-10 Configuring Static NAT Router(config)#ip nat inside source static 192.

200.1.255 Router(config)#ip nat pool isp-pool 209.0 0.165. the router can provide host machines with configurations such as an IP address.0.qxd 7/28/06 8:56 AM Page 109 Day 15 109 Example 15-13 Configuring NAT with Overload for One Outside IP Address Router(config)#access-list 1 permit 192. As a DHCP server.255 Router(config)#ip nat inside source list 1 interface serial 0 overload Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside You can also configure NAT with overload to translate a pool of addresses using the following commands: access-list access-list-number permit inside-network wildcard-mask ip nat pool pool-name start-IP-address end-IP-address netmask netmask ip nat inside source list access-list-number pool pool-name overload ip nat outside ip nat inside Example 15-14 Configuring NAT with Overload for a Pool of Outside IP Addresses Router(config)#access-list 1 permit 192.200.0.255.4—You can configure a router to handle host addressing on your LAN with DHCP.224 Router(config)#ip nat inside source list 1 pool isp-pool overload Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside 1.235 netmask 255. and lease time.1.165. .0 0.5—You can verify NAT and PAT configurations with the following commands: show ip nat translations show ip nat statistics show running-config 1.1.0.168.225 209.168.0. a DNS server.20_1587131749_DAY15.2.255.6—You can also watch every packet that is translated in NAT with the following commands: debug ip nat debug ip nat detailed 1.1.

com You can exclude a range of addresses or a single address from the DHCP pool that you wish to reserve and assign to specific hosts with the following commands: ip dhcp excluded-address start-address end-address ip dhcp excluded-address single-address Example 15-16 DHCP Pool Excluded Address Range or Specific Addresses Router(config)#ip dhcp pool excluded-address 192.168.20_1587131749_DAY15.2.5—To configure DHCP on a router. use the show ip dhcp binding command.qxd 110 7/28/06 8:56 AM Page 110 31 Days Before Your CCNA Exam 1.0 255.4.254 You can start and stop the DHCP service with these two commands: service dhcp no service dhcp 1.1 192. Example 15-17 Displaying DHCP Bindings Router#show ip dhcp binding You can also verify that the router is sending and receiving DHCP messages with the show ip dhcp server statistics command. which is shown in Example 15-18.168.4.7—To make sure that DHCP is operating.2.4.168. .168.254 Router(dhcp-config)#dns-server 192.2 Router(dhcp-config)#netbios-name-server 192.0 Router(dhcp-config)#default-router 192.4. which is shown in Example 15-17.6 and 1.2.255.168.3 Router(dhcp-config)#domain-name bennettsupport.20 Router(config)#ip dhcp pool excluded-address 192.168.4. you first define the DHCP pool and then provide other TCP/IP parameters with the following commands: ip dhcp pool pool-name network network-address subnet-mask default-router default-router-address dns-server dns-server-address netbios-name-server netbios-name-server-address domain-name domain-name Example 15-15 Configuring DHCP Router(config)#ip dhcp pool subnet4 Router(dhcp-config)#network 192.4. Make sure that you test all show commands in a lab or simulation so that you are familiar with the output.4.255.168.

20_1587131749_DAY15.2.8—If you have a DHCP server in a different network and would like DHCP broadcasts to for- ward across a subnet on a router. Module 6 6. Example 15-19 Displaying DHCP Processes Router#debug ip dhcp server events 1.2.168.1 CCNA 4. which is shown in Example 15-19.qxd 7/28/06 8:56 AM Page 111 Day 15 111 Example 15-18 Displaying DHCP Message Count Router#show ip dhcp server statistics If you would like to see information about addresses returned and allocated as well as address lease information.7—If you have a Simple Network Management Protocol (SNMP) server running on your net- work and you would like to enable SNMP on your router. use the debug ip dhcp server events command. you can use the following commands: snmp-server community community-string {ro | rw} snmp-server location location snmp-server community contact . as shown in Example 15-20.17. you can use the ip helper-address command. This command allows you to configure a router to forward the following services: ■ Time ■ Terminal Access Controller Access Control System (TACACS) ■ Domain Name Service (DNS) ■ Bootstrap Protocol (BOOTP)/DHCP Server ■ BOOTP/DHCP Client ■ Trivial File Transfer Protocol (TFTP) ■ NetBIOS Name Service ■ NetBIOS Datagram Service Use the following command to forward a DHCP broadcast: ip helper-address address Example 15-20 Forwarding DHCP Broadcasts Across a Router Router#ip helper-address 192.

exam #640-801). You can benefit greatly from the advantages of using internal private addressing from both an expense and security standpoint. You can review some of these concepts in pages 475–486 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.20_1587131749_DAY15. and PAT all provide additional functionality for your router. Your Notes . NAT.qxd 112 7/28/06 8:56 AM Page 112 31 Days Before Your CCNA Exam Example 15-21 Enabling SNMP on a Router Router(config)#snmp-server community campus3 ro Router(config)#snmp-server location building1A Router(config)#snmp-server contact Matt S. DHCP. 555-1234 The ro and rw options stand for read only and read write. Summary Passwords for router access. Second Edition.

1Q is an open standard. A VLAN can be as small as a department or as large as an entire building. The switch configured for static VLANs should also be in VTP server mode. Although it is possible to assign VLANs based on job function.2. it is most common to assign VLANs based on geographic location. you review the syntax for VLAN and VTP configuration commands and see examples of how the commands should look in the command-line interface (CLI). as corporations work to centralize network resources. ISL is a Cisco proprietary protocol. Today. ■ VLAN 1 must carry VLAN Trunking Protocol (VTP) and Cisco Discovery Protocol (CDP) traffic. You also need to adhere to the following requirements of VLAN 1: ■ VLAN 1 is one of the factory default VLANs.2. ■ You plan to control any and all moved workstations.1 and 8. Consider today’s information a primer for hands-on review in the lab or with a simulator. 8.qxd 7/28/06 8:56 AM Page 113 Day 14 Configure a Switch with VLANs and Interswitch Communication Switches allow you to completely restructure your network design with a couple of keystrokes.2. Virtual LANs (VLANs) and the VLAN Trunking Protocol (VTP) allow you to avoid the myriad ports and Category 5 cable that your hub-wielding predecessors battled during their attempts to segment and scale a network.3—You would configure static VLANs if your network design fits the following description: ■ You have VLAN software to configure ports. The flexibility of VLAN implementation provides the following features: ■ VLAN membership based on job assignment regardless of location ■ VLAN membership that follows the users when they change location on the network ■ VLAN membership that provides security settings assigned for each logical group You can configure switches to share VLAN information with frame tagging using Inter-Switch Link (ISL) or Institute of Electrical and Electronics Engineers (IEEE) 802.21_1587131749_DAY14. while IEEE 802. ■ You do not want to manage by MAC address. By default.2—VLANs allow you to logically separate a network into Layer 3 subnets. the switch’s IP address is in the VLAN1 broadcast domain. . CCNA 3.1Q. Module 8 8. ■ VLAN 1 must be the default Ethernet VLAN. Amazing. Modules 8 and 9 from CCNA 3 explain the concepts and configurations behind VLANs and VTP.

The commands to create a VLAN and apply the VLAN to interfaces in global configuration mode are as follows: vlan vlan-number interface interface switchport mode access switchport access vlan vlan-number Example 14-2 Configuring a VLAN in Global Configuration Mode Switch#configure terminal Switch(config)#vlan 2 Switch(config-vlan)#exit Switch(config)#interface fastethernet 0/4 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 2 8.21_1587131749_DAY14.2. 8. you can use the show running config and show vlan commands to capture VLAN configuration settings with the text capture .5—If you created your VLAN in global configuration mode.qxd 114 7/28/06 8:56 AM Page 114 31 Days Before Your CCNA Exam The commands to create a static VLAN using the vlan database command and apply the VLAN to interfaces are as follows: vlan database vlan vlan-number interface interface switchport access vlan vlan-number Example 14-1 Configuring a VLAN Using the vlan database Command Switch#vlan database Switch(vlan)#vlan 2 Switch(vlan)#exit Switch#configure terminal Switch(config)#interface fastethernet 0/4 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 2 VLAN configuration is now preferred in global configuration mode rather than using the vlan database command.2.4—The following commands allow you to verify your VLAN configuration: show vlan show vlan brief show vlan id {id | name} vlan Remember that all ports are in VLAN1 by default.

Trunking protocols allow switches to send information from multiple VLANs across a single channel. Example 14-3 Deleting a VLAN Using the vlan database Command Switch#vlan database Switch(vlan)#no vlan 2 Switch(vlan)#exit Example 14-4 Deleting a VLAN in Global Configuration Mode Switch#configure terminal Switch(config)#no vlan 2 CCNA 3. As mentioned previously. To look at the type of trunking configured on a Catalyst 2900.4—A trunk between switches is a physical and logical connection that passes network traffic.1.6—To remove a VLAN. the two types of frame tagging are the Cisco proprietary ISL and IEEE 802. A switch uses frame tagging to add header information to each frame identifying the VLAN ID of that frame for other switches connected through a trunk link.21_1587131749_DAY14. as shown in Examples 14-3 and 14-4.qxd 7/28/06 8:56 AM Page 115 Day 14 115 feature in HyperTerminal. You can also back up your VLAN configuration with the following command: copy running-config tftp 8.1. Module 9 9.1.2. The IEEE has defined frame tagging as the standard trunking type. 9. use the following command: show trunk module/port .1Q.1–9. you do not need this command because 802.1Q is the only encapsulation available. Two types of trunking protocols are frame filtering and frame tagging.5—The following command configures trunking on a Catalyst 2900 switch: switchport trunk encapsulation {isl | dot1q} Example 14-5 Configuring VLAN Trunking on a 2900 Switch(config)#interface fastethernet 0/12 Switch(config-if)#switchport trunk vlan isl On a Cisco Catalyst 2950. you use the no statement at the beginning of the VLAN configuration command. The trunk link provides a single backbone connection for multiple VLANs between switches.

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Make sure that you use all the show commands in this book when you are practicing in a lab
or simulation so that you are familiar with the output.
9.2.1–9.2.3—VTP allows you to manage your VLANs with Layer 2 trunk frames. You can add,

delete, and rename VLANs using VTP. You can configure VLANs to be encapsulated in ISL or
802.1Q frames. VTP messages always contain the following items:

VTP protocol version

VTP message type

Management domain length

Management domain name

Table 14-1 outlines the three possible modes for a VTP switch.
Table 14-1

VTP Switch Modes

VTP Mode

Capabilities

Definition

Server

Can create, modify, and delete VLANs

Sends VTP messages out all trunk ports and
saves VLAN configuration in the NVRAM.

Client

Cannot create, modify, and delete VLANs

Better for switches that do not have enough
memory for large configurations. VTP clients
process changes and forward messages.

Transparent

Only forwards advertisements

Forwards the messages, but does not modify its
own independent VLAN database.

VLAN modifications occur only in the VTP domain where they originate. The configuration revision number of a VTP update determines whether or not a switch will overwrite its database. The
switch overwrites its database information using the most recent update with the highest configuration revision number. VTP maintains its own NVRAM, and the configuration register can only be
reset if you clear the NVRAM and reboot the switch. By default, VTP does not operate in secure
mode.
9.2.4—Switches use VTP to multicast the following information:

Management domain

Configuration revision number

Known VLANs

Known VLAN parameters

Once you have set up a VTP domain, you need to configure only one device, and all the other
devices learn from this device. VTP advertisements start with the configuration register number 0,
increase by 1 until they reach 2,147,483,648, and then start again at 0. VTP advertisements are
either a request from a client or a response from a server. The three types of VTP messages are as
follows:

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Advertisement requests—Clients request VLAN information.

Summary advertisements—The switch sends summary advertisements every five minutes.
A switch updates its database only if the configuration revision number is higher than the
switch’s current revision number.

Subset advertisements—Subset advertisements are triggered by changes to VLAN settings
such as creation or deletion. These advertisements provide specific information about
VLANs.

9.2.5—To set up VTP, you need to configure the version number, the VTP domain, the VTP

mode, and a password with the following commands:
vlan database
vtp v2-mode
vtp domain domain
vtp {client | server | transparent}
vtp password password

Example 14-6

Configuring a VTP Server

Switch#vlan database
Switch(vlan)#vtp v2-mode
Switch(vlan)#vtp domain group3
Switch(vlan)#vtp server
Switch(vlan)#vtp password cisco

Once you have completed the VTP configuration, you can quickly check it with the following
commands:
show vtp status
show vtp counters

9.3.2–9.3.6—You need to use a Layer 3 router in order to allow devices to communicate across
VLANs. You can connect a physical router interface to each VLAN just as you would connect
router interfaces to separate switches, or you can use one physical interface and configure logical
subinterfaces for each VLAN. If your router has one 100 Mbps connection to a switch with
VLANs 1, 20, and 30, you can configure the interface with the following commands for each
subinterface:
interface fastethernet slot-number/port.subinterface-number
encapsulation dot1q vlan-number
ip address ip-address subnet-mask

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Example 14-7

Router VLAN Subinterface Configuration

Router(config)#interface fastethernet 0/0.1
Router(config-if)#encapsulation dot1q 1
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config)#interface fastethernet 0/0.2
Router(config-if)#encapsulation dot1q 20
Router(config-if)#ip address 192.168.2.1 255.255.255.0
Router(config)#interface fastethernet 0/0.3
Router(config-if)#encapsulation dot1q 30
Router(config-if)#ip address 192.168.3.1 255.255.255.0

In Example 14-7, as always, VLAN1 is the management VLAN. It cannot be deleted and carries
VTP and CDP.

Summary
Most switches work right out of those cool Cisco shipping boxes, but a true CCNA (or CCNA in
training) would strive to implement the additional features available in a switch. You can divide the
network logically with VLANs and then push that configuration across multiple switches with
VTP. Another source for review of today’s material can be found in pages 111–120 and 350–386
in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study, exam #640-801), Second
Edition.

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If you use 100 Mbps switches.2. CCNA 1.000. Table 13-2 provides bandwidth specifications for devices.1–2.2. Modules 2. Table 13-2 Bandwidth Units Media Type Bandwidth in Mbps Maximum Distance 10Base2 Ethernet Thinnet. Table 13-1 displays the units you use to describe bandwidth.7—Bandwidth represents the amount of data you can transfer over a network. and 7 from CCNA 1 provide information about LAN implementation. and you typically need to purchase bandwidth for your WAN connection.qxd 7/28/06 8:56 AM Page 121 Day 13 Implement a LAN Today’s objective. this objective provides a good opportunity to talk about some LAN topics. Coaxial 10 185 meters 10Base5 Ethernet Thicknet. Coaxial 10 500 meters 10BaseT Ethernet Category 5 UTP 10 100 meters 100BaseTX Ethernet Category 5 UTP 100 100 meters 1000BaseTX Ethernet Category 5 UTP 1000 100 meters 100BaseFX Ethernet Multimode Optical Fiber 100 or 1000 220 meters 1000BaseSX Ethernet Multimode Optical Fiber 1000 550 meters 1000BaseLX Ethernet Singlemode Optical Fiber 1000 5000 meters . 4. 5. and maximum distance.000 bits per second Gigabits per second Gbps 10 bits per second Terabits per second Tbps 10 bits per second 9 12 Category 5 (Cat 5) unshielded twisted pair (UTP) copper cabling is presently physically limited to 1 Gbps. implementing a LAN. Table 13-1 Bandwidth Units Unit Abbreviation Comparison Bits per second bps This is the base unit Kilobits per second kbps 1000 bits per second Megabits per second Mbps 1. that do not fit well elsewhere. but the devices and signaling type that you implement in a LAN determine the actual bandwidth.22_1587131749_DAY13. seems about as easy to pin down for details as implementing world peace. such as bandwidth and cabling. your LAN will operate at 100 Mbps. Module 2 2. LAN bandwidth is faster than WAN bandwidth. maximum bandwidth. However.

Do not confuse megabits per second with megabytes. ■ Insertion loss—The combination of attenuation and impedance effect on a signal.1—Your network cabling will likely include one or many of the types of cable outlined in Table 13-3.2. number of users. Noise can be any electrical source that distorts the signal on a cable.2. and power conditions can affect throughput. Table 13-3 Cable Types Cable Type Use Features Coaxial Thicknet and Thinnet Shielded. single copper wire. Pay keen attention to the use of bits in bandwidth measurement and not bytes. it is important to consider sources of noise that can affect your signal. Noise that originates from other cables or wires is defined as crosstalk.5—When you run cable for a LAN. It would take 8 seconds in perfect conditions to transfer 1 MB of data over a 1 Mbps connection.2—The following three terms define factors that can affect network signals: ■ Attenuation—The decrease in the strength of a signal as it travels across physical media. yet inexpensive and easy to install Shielded twisted pair (STP) Network installations where noise exists and fiber is less practical IBM-specific cable with two conductors individually covered with grounded foil shielding inside of braided shielding for the entire cable Screened twisted pair (ScTP) Network installations where noise exists and fiber is less practical Category 5 cable with grounded foil shielding.3–4. capable of longer distances. One byte is equal to eight bits. Table 13-4 outlines different types of crosstalk. 4. . Module 4 4. devices. CCNA 1. more expensive than UTP Fiber-optic Long-distance and/or high noise network installations Not affected by electrical noise.qxd 122 7/28/06 8:56 AM Page 122 31 Days Before Your CCNA Exam The maximum bandwidth may be different from the actual throughput on your network. The type of data. more expensive and difficult to install than UTP Unshielded twisted pair (UTP) Common network installation cable No shielding.2. more expensive than UTP 4. A bad connection or cable discontinuity can result in signal echoes causing signal jitter. You typically use bytes and megabytes to describe file sizes.2. ■ Impedance—The resistance of the physical media that can cause a signal to attenuate.22_1587131749_DAY13.

qxd 7/28/06 8:56 AM Page 123 Day 13 Table 13-4 123 Noise Type Definition Near-end crosstalk (NEXT) Crosstalk from another wire pair on the same end of the link Far-end crosstalk (FEXT) Crosstalk on the far end of the link. or rollover UTP cable.22_1587131749_DAY13. straight-through. configuration. less significant due to attenuation Power sum near-end crosstalk (PSNEXT) The effect of NEXT from all wire pairs in a cable The TIA/EIA-568-B standard requires a cable to return acceptable levels for ten cable parameters including NEXT. and PSNEXT. Table 13-5 UTP Cabling for Network Devices Cable Used to Connect Description Crossover cable Switch to switch TIA/EIA-568-A on one end and TIA/EIA-568-B on the other end. FEXT. Often converted to 9-pin port on a device for serial on one end. Switch to hub Hub to hub Router to router Host/server to host Router to host Straight-through cable Router to switch TIA/EIA-568-A on both ends or TIA/EIA-568-B on both ends.5 and 5.2. typically a serial port on a host to a console port on a router or switch . Module 5 5. Router to hub Host/server to switch Host/server to hub Rollover cable Terminal to console Pins 1–8 reversed on either end. CCNA 1.1.7—Table 13-5 explains when you would use a crossover.

Remember that noise can render a network unusable and your data unreadable if you cable your LAN incorrectly. 10Base2.22_1587131749_DAY13.1–7. 1000BaseSX. Combine your knowledge of switching and cabling to answer pages 52–92 in the CCNA Flash Cards and Exam Practice Pack (CCNA SelfStudy.1—10Base5. The type of cable you use dictates the distance and maximum bandwidth of your link. exam #640-801). For longer cable standards.1. and 1000BaseLX. Remember that UTP copper cabling can run only 100 meters between devices. and 10BaseT are legacy 10 Mbps Ethernet standards that you would likely replace with 100 Mbps 100BaseTX Fast Ethernet or 1000BaseTX Gigabit Ethernet. Module 7 7. Summary UTP now rules the LAN in most situations.qxd 124 7/28/06 8:56 AM Page 124 31 Days Before Your CCNA Exam CCNA 1.2. you would use 100BaseFX. Your Notes . Second Edition.

switching modes.3. . but you need a router to communicate between VLANs. consider the following three points when placing and configuring network devices: ■ Bridges and switches divide collision domains and filter at Layer 2. Routers have enough network knowledge to respond to broadcasts for their connected segments and thus to filter broadcasts. You have covered the specifics of these concepts and configurations on Day 14. “Perform an Initial Configuration on a Router and Perform an Initial Configuration on a Switch (Two Objectives).2. Module 4 4. and subinterface configurations all provide the means to customize a switch configuration for your specific network requirements.6—If you connect any number of computers to a hub.” and you will cover the initial configuration of a switch on Day 11. When you implement a LAN. You can divide this single collision domain with a switch and keep local traffic local because the switch filters based on the MAC address. ■ Layer 2 switches can also divide broadcast domains with VLANs.” Customize a Switch Configuration to Meet Specified Requirements Static and dynamic virtual LAN (VLAN) assignment. Each port on a bridge or switch is microsegmented into its own collision domain. those computers all see each other and have to deny or accept every transmission that occurs on that network.qxd 7/28/06 8:57 AM Page 125 Day 12 Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives) Today and on Day 11 you cover two objectives in one day. “Configure a Switch with VLANs and Interswitch Communication.23_1587131749_DAY12.1–4.9 and 4.” Today you focus on switch placement and layered model references found in Modules 4 and 5 from CCNA 3.2. The super short switch configuration customization objective fits nicely with the longer system image and configuration file management objective. Virtual Terminal Protocol (VTP). ■ Layer 3 switches and routers filter at Layer 3 of the OSI model and divide broadcast domains. CCNA 3. The only time that all devices see a transmission is when a host needs to ask all other hosts for information in the form of a broadcast. Not to mention that “31 Days to the CCNA” sounds a lot better than “33 Days to the CCNA.

it is a great idea to back up your configurations. Module 5 5.1.qxd 126 7/28/06 8:57 AM Page 126 31 Days Before Your CCNA Exam CCNA 3.23_1587131749_DAY12. you will likely decide to upgrade your network device software. Modules 3 and 5 from CCNA 2 provide the information to accomplish these tasks.1 to 192. or a disk. CCNA 2.2.8 and 3.80 [confirm] y Writing configbackup. make sure you know the IP address of the TFTP server and use the following command: copy running-config tftp {enter host IP address} {type a name for the configuration file} {type y} Example 12-1 Back Up a Configuration to a TFTP Server Router#copy running-config tftp Remote host []?192.1. As new security threats surface and new software features emerge. use the following commands: copy tftp running-config {select a host or network configuration file} {enter host IP address} {type the name of the configuration file} {type y} .168.168. a network server.6—Although there are beefy switches at the core layer of a network and Layer 3 switches at the distribution layer.80 Name of configuration file to write [Router-config]?configbackup.2.1 !!!!!! [ok] To restore the file to your router. Module 3 3.2. To save your router configuration to a TFTP server.1 Write the file configbackup. Manage System Image and Device Configuration Files After you configure your network and everything functions properly. How you want a user to connect to the distribution layer will determine the specific configuration of your switches. you will spend most of your time configuring VLANs and VTP at the access layer of your network.1–5.2.9—You can store a configuration file on a TFTP server.

1.23_1587131749_DAY12. the router first looks for a configuration file in the NVRAM.1 !!!!!!!!!!!!!! 752 bytes copied in 8. The commands will be visible in the running-config and startup-config (if saved) and are only used when the register value is set (see Table 12-1).1. loads a stripped version of the IOS image from ROM.3—You can define where a router should look for the IOS by entering boot system commands in global configuration mode. 5. The router first looks for the Cisco IOS image in the flash memory. Once the IOS image is loaded.2 and 5.qxd 7/28/06 8:57 AM Page 127 Day 12 Example 12-2 127 Restore a Backup Configuration from a TFTP Server Router#copy tftp running-config Address or name of remote host []? 192. 3.1. Module 5 5.168. and lastly.03 secs Router# You can also copy the output of the show run command from your terminal and paste it into a text file to back up a configuration.80 Router(config)#boot system rom Router(config)#exit Router#copy running-config startup-config .168.1. if there is no configuration.1—A router starts using the following sequence: 1. 2. and finally. then looks for a TFTP server that might have the configuration.80 Source filename []? Configbackup. boot system flash IOS-filename boot system tftp IOS-filename tftp-address boot system rom Example 12-3 Boot System Commands Router(config)#boot system flash myios-image Router(config)#boot system tftp myios-image 192. The order in which you enter the commands will define the order in which the router will use them to find an IOS image.168. CCNA 2. if there is no other option.1. then looks for a TFTP server that could have the IOS image.1 Destination filename [running-config]? running-config Accessing tftp://192.80/configbackup. The router checks the hardware (POST) and loads the bootstrap code from the read-only memory (ROM). outputs a set of questions to the console to ask the user for configuration parameters.1. The purpose of these boot system commands is to override the router’s default configuration register.

5—Use the following command to check the configuration register value and the boot image source: show version If you would like to check the boot system commands.qxd 128 7/28/06 8:57 AM Page 128 31 Days Before Your CCNA Exam 5. The parameters for an IFS management command are as follows: copy location:URL location:URL Example 12-5 Copy a Configuration File with TFTP Using IFS URL Conventions Router#copy tftp://192.1—Cisco IOS release 12. and the following command will allow you to change the configuration register: config-register configuration-register-value Example 12-4 Change the Configuration Register Router(config)#config-register 0x2102 Table 12-1 displays the values and descriptions for the configuration register.23_1587131749_DAY12. the system boots the first image in flash.168. The IFS allows you to follow a single command convention to manage the file system. Use b to boot the system. 0x___2 to 0x___F 0x2142 Looks in the NVRAM for boot system commands. 0x___1 0x2101 Boots the first image in flash.1. If there are no commands.0 and later releases use the Cisco IOS File System (IFS).1. 5. use the following show command: show running-config 5.4—You can also define how a router should boot by editing the configuration register in the NVRAM. This setting will boot the limited ROM version on older platforms. The show version command will display the current settings.1. NVRAM.80/backup-config system:running-config RAM. and flash hold the following configuration files: ■ Running configuration—Contained in the RAM ■ Startup configuration—Contained in the NVRAM ■ Cisco IOS image—Contained in flash .2. Table 12-1 Configuration Register Values Register Value Example Description 0x___0 0x2100 System enters ROM monitor mode.

1 Release 3) File Format (Relocatable. You should first use the following ROMMON commands to check your Cisco IOS image file and ensure proper boot settings: dir flash: boot flash: image-name . Not Compressed) Feature Set (Enterprise with Extended Capabilities) Hardware Platform (2600) 5.168. you can use ROM monitor (ROMMON) mode to restore the image.168.qxd 7/28/06 8:57 AM Page 129 Day 12 129 5.2. Figure 12-1 A Cisco IOS Name Example c2600-js-l_121-3.2—Figure 12-1 provides an example for the IOS naming convention.5—The following commands back up a Cisco IOS image: copy flash tftp {enter the source filename} {enter TFTP server IP address} {enter or select the destination file name} Example 12-6 Back Up a Cisco IOS Image to a TFTP Server Router#copy flash tftp Source filename []? c2600-is-mz Address or name of remote host []?192.1.6—If your router has a corrupted or missing IOS.2.80 Destination filename [c2600-is-mz]? c2600-is-mz-jan06 The following command allows you to restore a Cisco IOS image: copy tftp flash {enter TFTP server IP address} {enter the source filename} {enter or select the destination file name} Example 12-7 Restore an IOS Image from a TFTP Server Router#copy tftp flash Address or name of remote host []?192.1.80 Source filename []? c2600-is-mz-jan06 Destination filename [c2600-is-mz]? c2600-is-mz 5.2.bin Version and Release Numbers (Version 12.23_1587131749_DAY12.

bin rommon 2>tftpdnld If the set command displays incorrect variables.23_1587131749_DAY12. 5. 5.10 IP_SUBNET_MASK=255. you will need to use your terminal program (HyperTerminal) to send the image that you have saved on your computer. In ROMMON mode. first use the confreg command to check your connection settings and then use the following xmodem command: xmodem -c image-file-name Example 12-8 Restore a Cisco IOS Image Using xmodem rommon 2>xmodem -c c2600-is-mz.1.255.2.1.1 TFTP_SERVER=192.168. .0 DEFAULT_GATEWAY=192. The show flash command also shows the image and available flash in the router file system.2.1.168.7—You can also use ROMMON to restore an image from TFTP using the set command to view your connection variables and then the tftpdnld command to restore the image: set tftpdnld Example 12-9 Restore a Cisco IOS Image Using tftpdnld rommon 1>set IP_ADDRESS=192. you should check your configuration register and boot system commands with these two show commands: show version show startup-config If you do need to restore the image.255. you can set the variables by entering the variable name followed by an = and then the desired setting.qxd 130 7/28/06 8:57 AM Page 130 31 Days Before Your CCNA Exam If there is in fact an image in the flash and it boots properly with the ROMMON boot flash command.168.bin Once your router is ready to receive. The variables and the filename are case sensitive. you can use ROMMON and xmodem to copy the IOS through the console connection.8—You can check the current Cisco IOS image and amount of flash on a router with the show version command.80 TFTP_FILE=/jan06/c2600-is-mz.

Proper configuration and organized Cisco IOS image management are a sign of a prepared network engineer. Pages 259–274 of the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.23_1587131749_DAY12. Pages 350–386 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. exam #640-801). you will encounter numerous switching challenges.qxd 7/28/06 8:57 AM Page 131 Day 12 131 Summary From the layered design to the exact configuration of each port. Second Edition. Your Notes . Second Edition. These commands come in handy when you set up your systems and then again when a system has problems. The software abilities of switches to reconstruct and organize traffic flow provide you with the tools to face such custom challenges. exam #640-801). review these topics. might help you to check your knowledge of switch configuration customization.

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2.7—While logged in to the router. The initial configuration of a router and initial configuration of a switch represent the common tasks that you will perform when you take a Cisco networking device out of its box and add it to your network. The command configure terminal from privileged EXEC mode enters you into global configuration mode. the first command mode you enter is user EXEC mode. you cover two objectives in one day.2.6 and 2. CCNA 2.5—When you initially log in to a router. Typing the command exit takes you back one mode at a time. Perform an Initial Configuration on a Router Day 11 provides a quick overview of the housekeeping commands required to organize and begin setup on routers and switches. Module 2 2. pressing the Spacebar enables you to view the next screen. The clock command is a great way to try out the question mark (?).2. You can also type a command followed by a question mark (?) to see possible ways to complete the command. and the command prompt will change to a number symbol (#).24_1587131749_DAY11. Table 11-1 displays the editing commands that you may sometimes use and that you will always need to know for the CCNA exam. If the output is more than a page. you can enter a number of interface and specific configuration modes. 2. User EXEC mode allows you to execute commands that show the status of a router. If there is an error in a command. you can use the question mark (?) to see a list of available commands. A dollar symbol ($) at the beginning of a long line indicates that the line has been scrolled to the left. From global configuration mode. the caret symbol (^) will note where the command may have an error.qxd 7/28/06 8:57 AM Page 133 Day 11 Perform an Initial Configuration on a Router and Perform an Initial Configuration on a Switch (Two Objectives) Today. whereas typing end or using the key combination Ctrl-Z places you back at the privileged EXEC mode. Initial router configuration is spread throughout the curriculum. as on Day 12. . You can type enable to enter privileged EXEC mode. but Modules 2 and 3 from CCNA 2 focus on the key points necessary.

Module 3 3. Table 11-2 Cisco IOS Command History Keys and Commands Keystroke or Command Definition Ctrl-P or Up Arrow Repeat the last command Ctrl-N or Down Arrow Repeat the most recent command in the history buffer show history Display the command buffer terminal history size number Set the history buffer size terminal no editing Turn off advanced editing terminal editing Enable advanced editing CCNA 2. .1–3.24_1587131749_DAY11.7—Example 11-1 shows a sample initial configuration on a router (does not include a routing protocol).2.1.qxd 134 7/28/06 8:57 AM Page 134 31 Days Before Your CCNA Exam Table 11-1 Cisco IOS Editing Keys and Commands Keystroke or Command Definition Tab Automatically complete a command Ctrl-P or Up Arrow Repeat previously typed command Ctrl-A Move to the beginning of a command line Esc-B Move back one word Ctrl-B or Left Arrow Move back one character Ctrl-E Move to the end of the command line Ctrl-F or Right Arrow Move forward one character Esc-F Move forward one word Ctrl-Z Exit configuration mode terminal no editing Turn off advanced editing mode 2.2.8—Table 11-2 displays the keys and commands related to the Cisco IOS command history.

1 255. Welcome to RouterA # RouterA(config)#enable secret class RouterA(config)#line console 0 RouterA(config-line)#password cisco RouterA(config-line)#login RouterA(config-line)#exit RouterA(config)#line vty 0 4 RouterA(config-line)#password cisco RouterA(config-line)#login RouterA(config-line)#exit RouterA(config)#interface fa0/0 RouterA(config-if)#ip address 192. a switch has only VLAN 1 and no IP address.24_1587131749_DAY11.1 RouterA(config)#exit RouterA#copy running-config startup-config Perform an Initial Configuration on a Switch Many switches work perfectly on a small network without any additional configuration. Module 6 6.dat erase startup-config reload . VLAN 1 is also called the management VLAN. however.qxd 7/28/06 8:57 AM Page 135 Day 11 Example 11-1 135 Router Initial Configuration Example Router>enable Router#configure terminal Router(config)#hostname RouterA RouterA(config)#banner motd # Enter TEXT message.1.2—By default. To completely clear a switch. covered in Module 6 from CCNA 3.168. You can assign an IP address to a virtual interface in VLAN 1 for remote management. use the following commands: delete flash:vlan.255.168.2.1 and 6. You can.1.255. CCNA 3. End with the character ‘#’. add both security and better organization to your network by completing the initial configuration of a switch.0 RouterA(config-if)#description Main Office LAN RouterA(config-if)#no shutdown RouterA(config-if)#no shutdown RouterA(config-if)#exit RouterA(config)#ip host RouterA 192.2.

1 SwitchA(config)#copy running-config startup-config Example 11-4 provides the commands to implement a basic switch configuration on a Catalyst 1900.1.2 255.255.3—A switch maintains a MAC address table that you can view and clear with the following commands: show mac-address table clear mac-address table .2 255.24_1587131749_DAY11.qxd 136 7/28/06 8:57 AM Page 136 31 Days Before Your CCNA Exam Example 11-2 Clearing a Switch Configuration Switch#delete flash:vlan.1.1 6.1.168.168.dat Switch#erase startup-config Switch#reload Example 11-3 provides the commands to implement a basic switch configuration on a Catalyst 2950.168. Example 11-3 A Basic Switch Configuration on a Catalyst 2950 Switch>enable Switch#configure terminal Switch(config)#hostname SwitchA SwitchA(config)#line con 0 SwitchA(config-line)#password cisco SwitchA(config-line)#login SwitchA(config-line)#line vty 0 15 SwitchA(config-line)#password cisco SwitchA(config-line)#login SwitchA(config-line)#exit SwitchA(config)#enable secret class SwitchA(config)#interface VLAN 1 SwitchA(config-if)#ip address 192.168.0 SwitchA(config)#ip default-gateway 192. Example 11-4 A Basic Switch Configuration on a Catalyst 1900 Switch>enable Switch#configure terminal Switch(config)#hostname SwitchA SwitchA(config)#enable secret class SwitchA(config)#ip address 192.255.2.255.255.1.0 SwitchA(config-if)#no shutdown SwitchA(config-if)#exit SwitchA(config)#ip default-gateway 192.

2 of the CCNA 3 course.2.80 Destination filename [c2950-i6q4l2-mz.bin The commands in Example 11-8 allow you to back up your switch operating system on a Cisco Catalyst 2900 switch.bin Address or name of remote host []? 192.EA1.5—If you are concerned about users attempting to falsify Layer 2 information (MAC spoof- ing) on your network.4—The following command assigns a static MAC address to a port on a switch: mac-address-table static host-mac-address interface interface vlan vlan Example 11-5 Static MAC Address Configuration Switch(config)#mac-address-table static 0011.2.4455 interface FastEthernet 0/3 vlan 1 Use the command no in front of Example 11-5 to remove the static MAC address configuration. 6.24_1587131749_DAY11.EA1.121-13.qxd 7/28/06 8:57 AM Page 137 Day 11 137 6. Example 11-7 Back Up the Switch Software to a TFTP Server on a Cisco Catalyst 2950 Switch Switch#copy flash tftp Source filename []? c2950-i6q4l2-mz.121-13.EA1jan06.2.2233. 6.168.121-13. You should also be able to move the switch operating system to a TFTP server as a backup.2.6 and 6.bin]? c2950-i6q4l2-mz. The commands in Example 11-7 allow you to back up your switch operating system on a Cisco Catalyst 2950 switch.2. you can allow only one MAC address to be used per port with the following commands to enable port security: switchport mode access switchport port-security switchport port-security maximum {maximum-number-of-MACs-per-port} switchport port-security violation {restrict | shutdown} Example 11-6 Port Security Configuration Switch(config)#interface fastethernet 0/2 Switch(config-if)#switchport mode access Switch(config-if)#switchport port-security Switch(config-if)#switchport port-security maximum 1 Switch(config-if)#switchport port-security violation shutdown Port security is a good alternative to managing all MAC addresses on a network with static configuration unless you have no scruples and you are getting paid by the hour.1. .7—Make sure that any new switch you are adding to a network has a basic config- uration similar to the ones in section 6.

You can also get a quick quiz fix from the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.121-13. and addressing to a switch. Second Edition. hostnames. you should practice on a simulator or in a lab on different models. exam #640-801).121-13. Today.bin]? [press enter] Destination IP address or hostname []? 192.EA1. pages 205–210.24_1587131749_DAY11.EA1jan06. You can also quiz yourself with pages 211–238 from the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. The initial setup of a router provides you with a quick warm-up for the advanced commands that are not as intuitive.bin]? [press enter] A Catalyst 1900 switch requires you to use the configuration menu to download a new software image to your switch.qxd 138 7/28/06 8:57 AM Page 138 31 Days Before Your CCNA Exam Example 11-8 Back Up the Switch Software to a TFTP Server on a Cisco Catalyst 2900 Switch Switch#copy flash:c2950-i6q4l2-mz.EA1.121-13.1.EA1.168. you also covered slightly more than the initial configuration of a switch.80 Source filename []? c2950-i6q4l2-mz. Second Edition. Once you have skimmed through the process to add passwords. Example 11-9 Restore the Switch Software from a TFTP Server on a Cisco Catalyst 2950 or 2900 Switch Switch#copy tftp flash Address or name of remote host []? 192. exam #640-801).bin tftp Source filename [c2950-i6q4l2-mz.168.80 Destination filename [c2950-i6q4l2-mz.EA1. .121-13.bin Destination filename [c2950-i6q4l2-mz.bin Use the commands shown in Example 11-9 to restore the switch operating system.1. The Catalyst 1900 is not able to upload an image.121-13.bin]? c2950-i6q4l2-mz. Summary Configuring a hostname and initial passwords on a router should be as common to you as washing the dishes.121-13.EA1.

qxd 7/28/06 8:57 AM Page 139 Day 11 Your Notes 139 .24_1587131749_DAY11.

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255.0.25_1587131749_DAY10.” and Day 19. you will encounter short chapters that will allow you to review quickly and still have time for hands-on practice and practice exams.255. Day 25.qxd 7/28/06 8:57 AM Page 141 Day 10 Implement an Access List Ten days to the exam.0 and source-wildcard of 255. 2000–2699 AppleTalk 600–699 IPX 800–899 Extended IPX 900–999 IPX Service Advertising Protocol 1000–1099 You use the following commands to configure a standard access list and then to apply that access list to an interface: access-list ACL-number {deny | permit} source-address wildcard-mask ip access-group ACL-number {in | out} Example 10-1 Standard Access Control List Router(config)#access-list 25 deny 192.255 Router(config)#access-list 25 permit any Router(config)#int fa0/0 Router(config-if)#ip access-group 25 in The term any represents a source of 0. Module 11 11. and Day 3. 1300–1999 Extended IP 100–199.0. You can only assign .168.1. All of these days review the information covered in Module 11 of CCNA 2. Today provides the third installment of the access control list (ACL) quartet in this book. For this final countdown to the CCNA. You should also keep in mind that a default deny any exists at the end of all access lists. “Evaluate Rules for Packet Control.0.255.0. Table 10-1 Access Control List Number Specifications Protocol Range Standard IP 1–99. CCNA 2.1.0 0.” briefly covers ACL troubleshooting. Today you review ACL configuration. “Develop an Access List to Meet User Specifications.” discussed ACL design and theory. “Troubleshoot an Access List.3—Table 10-1 defines the range of numbers that you can use to define ACLs.

The following examples of extended ACLs display these additional filtering options: access-list ACL-number {deny | permit} protocol source wildcard destination wildcard operator port ip access-group ACL-number {in | out} Example 10-3 Extended Access Control List Filtering a Web Server Router(config)#access-list 101 deny tcp any host 192.0.1.1. and the Layer 4 protocol.168.1.255 192.168.23 eq www Router(config-ext-nacl)#permit tcp any any Router(config-ext-nacl)#exit Router(config)#int fa0/0 Router(config-if)#ip access-group filterweb in . The following commands allow you to configure a named ACL: access-list {extended | standard} name {deny | permit} protocol source wildcard destination wildcard operator port ip access-group acl-name {in | out} Example 10-4 Named Access Control List Filtering a Web Server Router(config)#access-list extended filterweb Router(config-ext-nacl)#deny tcp any host 192. you can use www or the port number 80 to represent the Layer 4 HTTP protocol.qxd 142 7/28/06 8:57 AM Page 142 31 Days Before Your CCNA Exam one access list per protocol per direction per interface.0. In Example 10-3. destination address.0.3—While standard access lists filter only the source IP address. You can use the following commands to configure an extended access list.168.5. access-list ACL-number {deny | permit} protocol source wildcard-mask destination wildcard-mask ip access-group ACL-number {in | out} Example 10-2 Extended Access Control List Router(config)#access-list 101 deny tcp 192.0. A named access list allows you to configure an alphanumeric name for an ACL and bypass the limits of numbering.0 0.0 0.1–11. an extended ACL can filter the source address.0.168.255 Router(config)#access-list 101 permit tcp any any Router(config)#int fa0/0 Router(config-if)#ip access-group 101 in 11.25_1587131749_DAY10.0 to match just one address.2.2.0.23 eq www Router(config)#access-list 101 permit tcp any any Router(config)#int fa0/0 Router(config-if)#ip access-group 101 in The term host in an access list substitutes the wildcard mask 0.

you need to design.qxd 7/28/06 8:57 AM Page 143 Day 10 143 11.1.2. You should apply the same restrictions to all vty lines. You should put a standard ACL as close to the destination of the traffic you are filtering as possible.30 Router(config)#line vty 0 4 Router(config-line)#access-class 5 in Summary To truly perform well on the access list portion of the CCNA exam. Spend some time in the Cisco IOS software at your lab or with a simulator to memorize the commands covered in this chapter.6—You can restrict vty access using access lists. It would also help to read through pages 456–476 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. remember to put an extended ACL as close to the source of the traffic you are filtering as possible. The following commands allow you to restrict vty access: access-list ACL-number {deny | permit} source-address wildcard-mask access-class ACL-number {in | out} Example 10-5 Restrict vty with an Access Control List Router(config)#access-list 5 permit host 192.25_1587131749_DAY10. The access-class command replaces the access-group command when configuring access lists for vty lines. . Second Edition.2. 11. document. exam #640-801).168. implement. and troubleshoot ACLs on a functioning or simulated network.4—As a quick reminder from Day 25.

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3—Use the following commands to set up PPP authentication: username name password secret-password encapsulation ppp ppp authentication {chap | chap pap | pap chap | pap} ppp pap sent-username username password password . Module 3 3.1 and 3. Today you review the configurations of the WAN technologies Point-to-Point Protocol (PPP). Module 1 1. error detection. and Frame Relay.3. dial-on-demand routing (DDR).3. Integrated Services Digital Network (ISDN). and 5 from CCNA 4 discuss WAN protocol configuration. Module 1 from CCNA 2 and Modules 3. and multilink features in PPP.3. CCNA 2.1. “Develop an Access List to Meet User Specifications.” and Day 19. and load balancing: encapsulation ppp compress {predictor | stac} ppp quality {1 to 100 as a percentage} ppp multilink Example 9-1 Enabling PPP Router(config)#interface serial 0/0 Router(config-if)#encapsulation ppp Router(config-if)#compress predictor Router(config-if)#ppp quality 50 Router(config-if)#ppp multilink 3. “Evaluate Key Characteristics of WANs. link quality. routers also function at Layer 3 to direct packets. CCNA 4. On a WAN.4—On a LAN.26_1587131749_DAY09.” you evaluated and selected routing protocols. routers choose the best path for Layer 3 packets across a network.qxd 7/28/06 8:57 AM Page 145 Day 9 Implement Simple WAN Protocols On Day 24. but they act as WAN devices as well and can require additional configuration to facilitate WAN connectivity. 4.2—You can configure authentication. compression. The following commands enable PPP encapsulation and configure compression.

framing type. The following commands allow you to set these parameters for an ISDN PRI T1: controller t1 framing {sf | esf} linecode {ami | b8zs | hdb3} pri-group timeslots range interface serial {slot/port: | unit:} {23 | 15} isdn switch-type switch-type .qxd 146 7/28/06 8:57 AM Page 146 31 Days Before Your CCNA Exam Example 9-2 PPP Authentication Router(config)#username cisco password class Router(config)#interface serial 0/0 Router(config-if)#encapsulation ppp Router(config-if)#ppp authentication chap pap Router(config-if)#ppp pap sent-username cisco password class 3.4—You can verify the PPP encapsulation configuration with the following command: show interfaces show interfaces serial CCNA 4.2—To configure ISDN PRI.1—You can configure ISDN to use the same switch type for all interfaces on the router.2. line coding. or you can specify the switch type for specific interfaces. Module 4 4. The following commands will configure ISDN to use the same switch type for all interfaces using BRI: isdn switch-type switch-type isdn spid{number} spid-number local-dial-number encapsulation ppp Example 9-3 ISDN BRI Configuration Router(config)#isdn switch-type basic-ni Router(config)#interface bri0/0 Router(config-if)#isdn spid1 51086750000001 8675000 Router(config-if)#isdn spid2 51086750010001 8675001 4.26_1587131749_DAY09. group timeslot. you specify the switch type as well as the controller. and speed.2.3.

3—The following commands allow you to verify your ISDN configuration: show isdn status show isdn active show dialer show interface 4. If the link comes up due to interesting traffic.26_1587131749_DAY09.qxd 7/28/06 8:57 AM Page 147 Day 9 Example 9-4 147 ISDN PRI T1 Configuration Router(config)#controller t1 1/0 Router(config-controller)#framing esf Router(config-controller)#linecode b8zs Router(config-controller)#pri-group timeslots 1-24 Router(config-controller)#interface serial3/0:23 Router(config-if)#isdn switch-type primary-5ess Router(config-if)#no cdp enable You would use the following commands to configure an ISDN PRI E1: controller e1 framing {crc4 | no-crc4} linecode {ami | b8zs | hdb3} pri-group timeslots range interface serial {slot/port: | unit:} {23 | 15} isdn switch-type switch-type Example 9-5 ISDN PRI E1 Configuration Router(config)#controller e1 1/0 Router(config-controller)#framing crc4 Router(config-controller)#linecode hdb3 Router(config-controller)#pri-group timeslots 1-31 Router(config-controller)#interface serial3/0:15 Router(config-if)#isdn switch-type primary-net5 Router(config-if)#no cdp enable 4.2–4. and PPP configuration: dialer-list number protocol protocol {permit | deny | list [access-list-number]} interface interface . an access list.3.2.3. You can define a dialer-list on a Cisco router that tells the router what traffic should cause it to bring up a DDR link.3. DDR configurations do not filter traffic. Access lists can also help you to better define interesting traffic. 4. You would use the following commands to create a basic configuration for legacy DDR including a static route. you need to use static routes to lower the cost of the route.1—Dial-on-demand routing (DDR) defines interesting traffic as network activity that causes a router to connect to a network. all traffic can pass over the link while it is active.5—To configure DDR.

1 name RouterB 8675309 Example 9-7 Legacy DDR Configuration with Access Lists RouterA(config)#ip route 192.26_1587131749_DAY09.1 name RouterB 8675309 4.2 RouterA(config)#dialer-list 1 protocol ip permit RouterA(config)#username RouterB password class RouterA(config)#interface bri0/0 RouterA(config-if)#dialer-group 1 RouterA(config-if)#encapsulation ppp RouterA(config-if)#ppp authentication chap RouterA(config-if)#dialer idle-timeout 180 RouterA(config-if)#dialer map 192.3. you can do the following: ■ Use different encapsulations and access lists ■ Set minimum and maximum calls ■ Enable and disable features You can add configurations to virtual dialer interfaces and then apply them to a pool of physical interfaces.0 192.255.168.3.168.1.0 255.0 255. With dialer profiles.3. router interfaces can apply the configuration on a per-call basis.1.2 RouterA(config)#dialer-list 1 protocol ip list 101 RouterA(config)#access-list 101 deny tcp any any eq ftp RouterA(config)#access-list 101 deny tcp any any eq telnet RouterA(config)#access-list 101 permit ip any any RouterA(config)#username RouterB password class RouterA(config)#interface bri0/0 RouterA(config-if)#dialer-group 1 RouterA(config-if)#encapsulation ppp RouterA(config-if)#ppp authentication chap RouterA(config-if)#dialer idle-timeout 180 RouterA(config-if)#dialer map 192.1.255.3.168.7—Legacy DDR applies the configuration to a specific interface.255.6 and 4.1.qxd 148 7/28/06 8:57 AM Page 148 31 Days Before Your CCNA Exam dialer-group number dialer idle-timeout seconds-after-last-traffic dialer map ip next-hop name next-hop-hostname dial-number Example 9-6 Legacy DDR Configuration Without Access Lists RouterA(config)#ip route 192. The following commands allow you to configure dialer profiles: dialer-list number protocol protocol {permit | deny | list [access-list-number]} interface dialer virtual-interface-number dialer-group number dialer remote name next-hop-hostname .168.255.168.168.0 192. If you use dialer profiles with DDR.

3.qxd 7/28/06 8:57 AM Page 149 Day 9 149 dialer string dial-number dialer-pool number dialer idle-timeout seconds-after-last-traffic dialer pool-member number priority priority Example 9-8 DDR Profile Configuration Without Access Lists RouterA(config)#ip route 192. Module 5 5.0 255.168.2.255.0 RouterA(config-if)#dialer-group 1 RouterA(config-if)#dialer remote name RouterB RouterA(config-if)#dialer string 8675309 RouterA(config-if)#dialer pool 1 RouterA(config-if)#interface bri0/0 RouterA(config-if)#encapsulation ppp RouterA(config-if)#ppp authentication chap RouterA(config-if)#dialer idle-timeout 180 RouterA(config-if)#dialer pool-member 1 priority 50 4.26_1587131749_DAY09.168.2 RouterA(config)#dialer-list 1 protocol ip permit RouterA(config)#username RouterB password class RouterA(config)#interface dialer 0 RouterA(config-if)#ip address 192. The following commands configure a basic Frame Relay permanent virtual circuit (PVC): encapsulation frame-relay {cisco | ietf} frame-relay map protocol protocol-address dlci broadcast . you can also use the Internet Engineering Task Force (IETF) standard encapsulation.1.255.255.0 192.2.3.8—The following commands allow you to verify your DDR configuration: show dialer show isdn active show isdn status CCNA 4.168. and the default encapsulation type is Cisco HDLC.1–5. Although many non Cisco routers support this encapsulation.5—You can configure your router for Frame Relay on a serial interface.255.1 255.1.

1 255.255.255.255.168. DLCI 131 RouterA(config-if)#ip address 192. you can configure subinterfaces.168.0.qxd 150 7/28/06 8:57 AM Page 150 31 Days Before Your CCNA Exam Example 9-9 DTE Frame Relay PVC Configuration Without a Frame Relay Switch (No Local Management Interface [LMI]) RouterA(config)#interface serial 0 RouterA(config-if)#encapsulation frame-relay ietf RouterA(config-if)#ip address 192.255.0 RouterA(config-if)#no shutdown RouterA(config-if)#no keepalive RouterA(config-if)#frame-relay map ip 192.131 point-to-point RouterA(config-if)#description PVC to Seattle.2 151 ietf broadcast RouterA(config-if)#description PVC to Portland.1 255.1.6—The following commands allow you to verify your Frame Relay configuration: show interfaces show frame-relay lmi show frame-relay pvc dlci-number show frame-relay map . DLCI 151 For multiple connections across a Frame Relay network. The following example shows a Frame Relay configuration with subinterfaces: encapsulation frame-relay {cisco | ietf} frame-relay lmi-type {ansi | cisco | q933a} interface serial {subinterface-number} {point-to-point | multipoint} frame-relay interface-dlci DLCI-number Example 9-10 Frame Relay Configuration with Subinterfaces RouterA(config)#interface serial 0 RouterA(config-if)#encapsulation frame-relay ietf RouterA(config-if)#frame-relay lmi-type ansi RouterA(config-if)#no shutdown RouterA(config-if)#interface serial 0.168. The subinterfaces can exist in their own subnet as point-to-point links.1 255.0 RouterA(config-if)#frame-relay interface-dlci 131 5.2.255.168.255.2. DLCI 130 RouterA(config-if)#ip address 192.0.26_1587131749_DAY09.130 point-to-point RouterA(config-if)#description PVC to Boise.0 RouterA(config-if)#frame-relay interface-dlci 130 RouterA(config-if)#interface serial 0. or you can configure the subinterfaces to share a single subnet as multipoint links.

DDR. You can also quickly test your knowledge with pages 511–574 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Second Edition. PPP. ISDN. exam #640-801). .26_1587131749_DAY09.qxd 7/28/06 8:57 AM Page 151 Day 9 151 Summary Although it is more difficult to find hands-on practice for WAN configurations. and Frame Relay configurations allow you to create complete networks that can span wide geographic areas. it is a good idea to at least work through simulations and practice the commands for the CCNA exam.

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qxd 7/28/06 8:57 AM Page 153 Part IV 8–1 Day(s) Before the Exam— Troubleshooting Day 8: Utilize the OSI Model as a Guide for Systematic Troubleshooting Day 7: Perform LAN and VLAN Troubleshooting Day 6: Troubleshoot Routing Protocols Day 5: Troubleshoot IP Addressing and Host Configuration Day 4: Troubleshoot a Device as Part of a Working Network Day 3: Troubleshoot an Access List Day 2: Perform Simple WAN Troubleshooting Day 1: Key Points From Each Day for Relaxed Skimming .27_1587131749_Pt4.

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Day 8
Utilize the OSI Model as a Guide for
Systematic Troubleshooting
The OSI seven-layer model allows you to chew a network into smaller, more digestible chunks.
This division also provides a great framework for troubleshooting. OSI model–related troubleshooting is discussed in Module 2 from CCNA 1; Modules 8, 9, and 10 from CCNA 2; and
Module 6 from CCNA 4.

CCNA 1, Module 2
2.3.3—Table 8-1 provides a quick review of the OSI seven-layer model.
Table 8-1

The Open System Interconnection Seven-Layer Model

Layer Number

Layer Name

Protocol Data Unit

Devices

7

Application

Data

N/A

6

Presentation

Data

N/A

5

Session

Data

N/A

4

Transport

Segment

N/A

3

Network

Packet

Router

2

Data link

Frame

Bridge, Switch

1

Physical

Bit

Hub, Repeater

CCNA 2, Module 8
8.1.5—You can test connectivity at OSI Layer 3 with the ping command. The ping command
issues an Internet Control Message Protocol (ICMP) echo request and then receives an echo reply
to verify connectivity. You typically issue the ping command followed by the IP address of the
destination device.

CCNA 2, Module 9
9.2.1—The OSI model provides an excellent structure for network troubleshooting. You can begin
at Layer 1 and work up to Layer 7 until you discover, solve, and document the issue.

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9.2.2—The following steps outline a typical troubleshooting model:
Step 1

Collect information and analyze the symptoms of the problem.

Step 2

Localize the problem to a segment of the network, device, or user.

Step 3

Isolate the problem to a specific piece of hardware or software.

Step 4

Correct the problem.

Step 5

Verify that the problem has been corrected.

Step 6

Document the problem.

Steps 2 through 4 can be incorporated with the OSI model by checking, fixing, and verifying each
layer, starting with Layer 1.
9.2.3–9.2.5—Problems at the first three layers of the OSI model are characterized by the following issues:

Physical layer (1)—Problems with cables and power. Cables in the wrong port, improperly
attached cables, and incorrect cable types are Layer 1 issues. Data terminal equipment (DTE)
and data communications equipment (DCE) cable problems or transceiver issues also qualify
as Layer 1 problems. Check all indicator LEDs and power LEDs before any other troubleshooting.

Data link layer (2)—Improper or missing configurations for clock rate and encapsulation
classify as Layer 2 issues. Serial and Ethernet configuration issues occur at Layer 2. Problems
with a NIC can also be considered Layer 2 issues.

Network layer (3)—IP addressing and routing protocol configuration issues occur at Layer 3.
Incorrect subnet masks also classify as Layer 3 issues. Problems identified with the ping
command (after testing Layers 1 and 2) are often Layer 3 issues. If you ping another device
and receive the ICMP destination unreachable message, the packet was not delivered. You can
use an extended ping command by typing ping without an IP address or hostname.

9.2.5—Telnet tests all seven layers of the OSI model. If you have a password configured for a vty

on your routers and you can telnet between them, all seven layers of the OSI model function on
your network. If you can ping a router but you cannot telnet to the router, you should first check
your vty setup.
9.2.6—If you issue the show interfaces command, Layer 1 issues are indicated by the line status.

If a router responds that the interface is down, it indicates that there is an issue with the cable or a
connected device.
9.3.1–9.3.3—The show interfaces command can also provide you with information about Layer

2 problems. If the show interface command for a serial interface returns that the serial 0/0 is
administratively down, you have not enabled the interface. A message that the interface is up but
the line protocol is down indicates a Layer 2 issue, such as keepalives on the link or improper
encapsulation. To verify connectivity at Layer 2 with Cisco devices, you can also use Cisco
Discovery Protocol (CDP). You review CDP on Day 7, “Perform LAN and VLAN
Troubleshooting.”

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CCNA 2, Module 10
10.1.3—A less obvious connectivity issue can occur at Layer 4 of the OSI model. The three-way

handshake that occurs at the transport layer is susceptible to a denial of service (DoS) attack carried out with continuous synchronization flooding. You can use software to monitor and detect
DoS attacks.

CCNA 4, Module 6
6.2.2 and 6.2.4—The OSI group also directed the development of a network management

model. This model deals with network management applications that operate at the transport and
application layers and often use Simple Network Management Protocol (SNMP) on Layer 4 port
161 and 162 User Datagram Protocol (UDP). The network information gathered by a management
information base (MIB) can provide valuable network statistics for troubleshooting and recognizing issues with OSI Layers 4 through 7.

Summary
A clear understanding of the seven layers of the OSI model aids your ability to describe a network
and to describe, document, and fix network issues. Although you covered them on Day 30,
“Describe the Spanning Tree Process,” it might not be a bad idea to return to pages 13–34 of the
CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study, exam #640-801), Second Edition
for some good old OSI review.

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Your Notes

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CDP is media and protocol independent and operates at the data link layer of the OSI model. The command clear cdp counters clears gathered CDP information.1. CDP gives you that extra layer of troubleshooting when ping and telnet yield unsatisfactory results. you can use the command cdp enable to start CDP on a specific interface. It is important to remember that the show cdp command shows information about the protocol only and that show cdp neighbors reveals information about connected devices.1. and 9 from CCNA 2 and Module 8 from CCNA 3. The Cisco Networking Academy Program covers methods for troubleshooting LANs and VLANs in Modules 4. Module 4 4.1. CDP version 2 (CDPv2) is the protocol running on devices with Cisco IOS Software Release 12.1. This makes your job a little easier when troubleshooting connectivity issues. This means you can properly connect and power up two Cisco devices and expect that they will exchange CDP advertisements over Layer 2 once you have enabled the interfaces with the no shutdown command and configured a clock rate for interfaces with a data communications equipment (DCE) cable attached. CDP uses the Subnetwork Access Protocol (SNAP) to communicate over a network with directly connected neighbors.3 and 4. CCNA 2.29_1587131749_DAY07. 4.2—The show cdp neighbors command reveals the following information about directly connected neighboring Cisco devices: ■ Device ID ■ Local interface ■ Holdtime ■ Capacity ■ Platform 4. you enable CDP on all interfaces on a device.1—All Cisco devices have CDP turned on by default. If you enter into interface configuration mode. 5.qxd 7/28/06 8:58 AM Page 159 Day 7 Perform LAN and VLAN Troubleshooting Cisco Discovery Protocol (CDP) is a great troubleshooting tool with Cisco devices.0(3)T or later.4—If you enter the command cdp run at the privileged EXEC prompt. The following commands will display information about CDP and CDP-enabled devices: show cdp traffic show cdp show cdp neighbors show cdp neighbors detail .

Module 5 5. Module 9 9.3—As mentioned in Module 4 of CCNA 2. . This command displays device details such as the following items: ■ Active interfaces ■ Port ID ■ Device type ■ Cisco IOS version ■ IP address of a neighboring device’s interface You have to bring the interface up with the no shutdown command and set a clock rate (if necessary) in order to receive CDP advertisements.5—The following two commands will turn off CDP globally or on a specific interface: no cdp run no cdp enable 4.1. Module 5 from CCNA 2 repeats this information and provides more detail on the use of HyperTerminal to capture a configuration. and monitor CDP activity on your Cisco device: clear cdp table show debugging debug cdp adjacency debug cdp events debug cdp ip debug cdp packets cdp timer cdp holdtime CCNA 2.6—The following commands allow you to view. you can use the menu items Transfer > Capture Text and then Transfer > Send Text to capture and then later place a configuration on a router. “Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives).29_1587131749_DAY07.2.qxd 160 7/28/06 8:58 AM Page 160 31 Days Before Your CCNA Exam You can use the show cdp neighbors detail command to reveal the most information.4—On Day 12.1.” you reviewed the backup of configuration files using a TFTP server discussed in Module 3 from CCNA 2.3 and 5.3. In HyperTerminal. including Layer 3 configurations of neighboring devices. 4. CCNA 2. the show cdp neighbors detail command is a very valuable tool.2. troubleshoot.

and show commands outlined today. Step 3 Check Layer 1. exam #640-801). Step 4 Check Layer 2. and naming: show vlan show spanning-tree debug sw-vlan packets If you are having trouble establishing a trunk connection between a router and a switch. your network could be experiencing broadcast storms.3. you can then check other parameters with the following show commands. If STP is running properly. Pages 240–258 and 383–386 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study.2—VLANs have become common in networks due to their ability to logically divide and organize traffic flow. You can use the following steps to troubleshoot VLANs: Step 1 Check LEDs and cables. Step 6 Look at traffic patterns and identify possible bottlenecks. you have a great toolkit to solve LAN and VLAN issues. might also be helpful as you prepare for the CCNA exam.3. protocols. Second Edition. Module 8 8. Step 5 Check VLANs that span multiple switches.3.3. Step 2 Pick one switch as a starting point and work outward.5—If Spanning Tree Protocol (STP) is not functioning properly.29_1587131749_DAY07. which allow you to look for errors in VLAN setup. 8. you can check the router interfaces and the Cisco IOS software trunking compatibility with the following commands: show interfaces interface trunk show interfaces interface switchport show interface status show running-config show version Summary If you use the OSI model as a reference and the cdp.1 and 8. .3–8.qxd 7/28/06 8:58 AM Page 161 Day 7 161 CCNA 3. debug.

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qxd 7/28/06 8:58 AM Page 163 Day 6 Troubleshoot Routing Protocols An advantage to using the command-line interface (CLI) of Cisco IOS software is your ability to use show and debug commands to obtain information about your network. including the Interior Gateway Routing Protocol (IGRP).7 and 7.1.30_1587131749_DAY06.1.0 ip route 0. show ip rip database show ip rip database Displays RIP updates.168.0.0 Sets a default route.0 0. show ip protocols .1–9. show ip route igrp show ip route static show ip route 192. The second example also defines a default route with a static route.1. show ip protocols Displays routing protocol information. The Cisco Networking Academy Program curriculum covers routing protocol–related troubleshooting commands in Modules 7 and 9 from CCNA 2 and in Modules 1.3.0.0.0 192. and 3 from CCNA 3.0 ip default-network ip default-network 192.0.5.168. 2.0/0 ip route 0. CCNA 2. Module 7 7.0. Module 9 9. Table 6-1 Routing Table–Related Troubleshooting Command Examples Definition show ip route show ip route rip Displays routing table information. whereas debug commands can display real-time routing protocol activity. The show commands can provide a valuable snapshot.3.168.0.8—The following commands allow you to verify and troubleshoot routing proto- cols.1. as a specific example: show interface show running-config show ip protocols show ip route debug ip igrp events debug ip igrp transactions ping traceroute CCNA 2.9—Table 6-1 provides a definition and examples of troubleshooting and configuration commands that pertain to the routing table.

Default administrative distances for common routing protocols are listed in Table 6-2.7—If you have configured Open Shortest Path First (OSPF) and the routers are not communi- cating. ■ Make sure that your interfaces are not on different network types. show ip protocols show ip route show ip interface brief show running-config debug ip rip It is also useful to know that the undebug all or no debug all commands turn off all debugging. Notice that the pattern of troubleshooting commands is similar for each protocol. Table 6-2 Default Administrative Distances Routing Protocol Default Administrative Distance Directly connected 0 Static 1 for a next hop IP address. Module 1 1.qxd 164 7/28/06 8:58 AM Page 164 31 Days Before Your CCNA Exam A quick look at the routing table can help you to determine which route has the lowest administrative distance.3. . you should consider the following possibilities: ■ Make sure that the neighbors are sending hellos.5 and 1. ■ Make sure that you do not have different hello and dead interval timers.6—The following commands allow you to verify and troubleshoot the Routing Information Protocol (RIP).30_1587131749_DAY06.2. CCNA 3. Module 2 2.2. 0 for an outgoing interface EIGRP summary route 5 eBGP 20 EIGRP (internal) 90 IGRP 100 OSPF 110 IS-IS 115 RIP 120 EIGRP (external) 170 iBGP 200 CCNA 3.

qxd 7/28/06 8:58 AM Page 165 Day 6 ■ Make sure that authentication is set up correctly. ■ If the plan does not work.30_1587131749_DAY06. ■ Make sure that you have issued the no shutdown command for each interface. change one thing at a time until you can isolate the problem.1—When you are troubleshooting routing issues. including wildcard masks. ■ Make sure that the addressing is set up correctly. EIGRP. Table 6-3 provides the common troubleshooting commands for RIP. CCNA 3. ■ Document the fix. consider the following points: ■ Clearly define the problem and gather all the related facts. IGRP. Module 3 3. and OSPF.3. Table 6-3 Troubleshooting Commands for Routing Protocols Routing Protocol Troubleshooting Commands RIP show running-config show ip protocols show ip route debug ip rip IGRP show running-config show ip protocols show ip route debug ip igrp debug ip igrp events EIGRP show running-config show ip protocols show ip eigrp neighbors OSPF show running-config show ip protocols show ip route show ip ospf neighbor debug ip ospf events debug ip ospf packet 165 . Expect some repetition in commands. ■ Create and implement an action plan.

30_1587131749_DAY06. exam #640-801). Your Notes . You can also pick out the troubleshooting command questions from pages 425–454 of the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Second Edition for a quick review.qxd 166 7/28/06 8:58 AM Page 166 31 Days Before Your CCNA Exam Summary The absolute best way to learn these commands is to have someone else royally mess up your network routing configurations and put you to work finding the errors.

To view all of your sessions.31_1587131749_DAY05.6—A quick way to test all seven layers of the OSI model is with the telnet command. you need to make sure that you have configured Domain Name System (DNS) or the ip host command on your router.qxd 7/28/06 8:58 AM Page 167 Day 5 Troubleshoot IP Addressing and Host Configuration When you understand the design and configuration of a network. simple commands such as ping and telnet provide great troubleshooting tools. You can specify up to five (0 through 4) vty sessions on a router to allow incoming Telnet connections to your router.1–4.2. you can type disconnect followed by the host or IP address.2.2 Example 5-2 Initiate a Telnet Session Using a Hostname Router#telnet RouterB You can suspend a Telnet session with the Ctrl-Shift-6. then x key combination.168. If you telnet to a router by hostname. you can type show sessions.0. The Cisco Networking Academy Program discusses IP addressing troubleshooting commands in Modules 4 and 9 of CCNA 2. you can test Layer 3 network connectivity using the following commands: ping traceroute show ip route . and to disconnect a specific session. The extended ping command on a router enables you to set very specific options when testing your IP configurations. CCNA 2. Module 4 4. If Telnet does not function. Telnet operates at the application layer of the OSI model and allows you to connect remotely to another router. The following command will initiate a Telnet session with another router: telnet {remote-router-ip-address | remote-router-hostname} Example 5-1 Initiate a Telnet Session Using an IP Address Router#telnet 192. You can resume a session by using the resume command followed by the host or IP address or by using the Enter key. All configurations and protocols have to function correctly to support a Telnet session.

2 Repeat count [5]: Datagram size [100]: Timeout in seconds [2]: Extended commands [n]:y Source address or interface:192. you type ping and press Enter and then specify the options shown in Example 5-3. Record. Module 9 9. exam #640-801).168.1 Type of service [0]: Set DF bit in IP header? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Loose. Verbose[none]: Sweep range of sizes [n]: Summary Often a mistyped IP address or incorrectly configured subnet mask proves to be the problem in a network that will not return a successful ping.0.qxd 168 7/28/06 8:58 AM Page 168 31 Days Before Your CCNA Exam CCNA 2.0.31_1587131749_DAY05. You could also flip through pages 255–258 in the CCNA Flash Cards book. This short chapter just begs you to take a CCNA practice exam today. Second Edition.168. Example 5-3 The Extended ping Command Router#ping Protocol [ip]: Target IP address:192.2. . Schedule a Cisco Networking Academy practice CCNA exam with your instructor or use the exam on the CD-ROM that accompanies the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Strict.5—To use the extended ping command. Timestamp.

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” and Day 7.32_1587131749_DAY04. You can also use the show version command to determine the Cisco IOS software version running on the router and what commands are supported. 4. be sure to delete unwanted text and add no shutdown to all configured interfaces.1.” as a review of key show. Before restoring a captured configuration. “Troubleshoot IP Addressing and Host Configuration. you can type that portion of the command followed by a question mark (?) to view the options for that command. Module 1 1.” you can quickly fix a configuration issue with a router by restoring an earlier running-config capture with your terminal program. Once you have verified Layer 3 connectivity. Step 2 Cycle through each layer of the OSI model to fix the problem starting at Layer 1. You can look for the carat symbol (^) to determine the portion of the command that the router did not understand. debug.2.” and Day 6. CCNA 2.2. These troubleshooting topics originate from Module 1 from CCNA 1 and Modules 2. Module 5 5.2.qxd 7/28/06 8:58 AM Page 171 Day 4 Troubleshoot a Device as Part of a Working Network Today combines with Day 5. Module 4 4. the ping and traceroute commands allow you to check Layer 3 connectivity on your network. and connectivity-related commands. “Customize a Switch Configuration to Meet Specified Requirements and Manage System Image and Device Configuration Files (Two Objectives).6—As mentioned on Day 5.4—As described on Day 12. Module 2 2. “Perform LAN and VLAN Troubleshooting.9—You can use the same basic steps to troubleshoot all network devices: Step 1 Collect information. . CCNA 1. CCNA 2. CCNA 2.5 and 4. some commands may not work. and 9 from CCNA 2. you can use Telnet to test all seven layers of the OSI model.2. 5. If part of the command was understood.2.10—As you troubleshoot a router. Step 3 Document your work.9 and 2. “Troubleshoot Routing Protocols.

Summary As mentioned yesterday.4–9.32_1587131749_DAY04. networks that are being advertised. The debug all command displays all events and uses system resources to the point that it should not be implemented on a production router.3. this command is useful. the source of routing updates. Debug can be processor intense and should be used only to troubleshoot. displays the type of cable that is connected and whether clocking is detected on the interfaces of the router. traceroute Identifies each hop on a path between two destinations. you can check configured routing protocols with the show ip protocols command. Pages 231–238 of the CCNA Flash Cards and Exam Practice Pack (CCNA SelfStudy. The command undebug all or no debug all turns off all debugging.7—Table 4-1 provides a list of some common troubleshooting commands and tactics: Table 4-1 Troubleshooting Commands Command Definition show ip route Allows you to view all information provided to the router through configured routing protocols. Second Edition also review these topics. show ip protocols Displays configured protocols. show controllers If a cable is connected. and interface events. The traceroute command allows you to isolate the interface that is dropping packets on a network. protocol events. If you are remotely connected to a router and cannot physically inspect the cables. terminal monitor Redirects debug information to a remote terminal session. including connected and known networks. you need to spend time using these troubleshooting commands to identify and fix network issues. Module 9 9. and which interfaces are sending updates.qxd 172 7/28/06 8:58 AM Page 172 31 Days Before Your CCNA Exam CCNA 2. Lab time or practice with a simulator will strengthen your knowledge of these topics.3. debug Shows events on the router as they occur. exam #640-801). including error messages. . If show ip route provides no information other than connected routes.

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Stand…standard. including whether an access list is assigned show access-lists Displays all access lists on a router show running-config Shows the entire running configuration.5—You can test your access lists by creating sample traffic on your network. Keep in mind that troubleshooting also requires you to review your design and protocols to check access list functionality. CCNA 2. a Cisco Academy online practice CCNA exam and then have somebody wreak havoc on an access list configuration for you to fix. . and you can verify access lists with the commands outlined in Table 3-1.33_1587131749_DAY03. exam #640-801). Summary Short day. including access list configurations 11.qxd 7/28/06 8:59 AM Page 175 Day 3 Troubleshoot an Access List The final installment in the review about access lists provides a list of show commands outlined in Module 11 from CCNA 2 that help you to see how the lists are configured.4—Where you place an ACL on a router can affect how it filters packets. Do not forget that all statements end with an implicit deny by default unless you specify otherwise. One way to remember this is to think that you always stand at your destination when you arrive.2. Pages 473–476 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Table 3-1 Access List show Commands Command Function show ip interface Displays interface information. or retake. Module 11 11.1. Second Edition can help you review today as well. ok…anyway. Remember that you place standard access lists as close to the destination of the traffic you want to filter and place extended access lists as close to the source of the traffic you want to filter. Take.

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it is important to note the protocol and concept that you are troubleshooting.5—To troubleshoot a serial connection. As you recognize these commands.qxd 7/28/06 8:59 AM Page 177 Day 2 Perform Simple WAN Troubleshooting Cisco IOS software provides a number of show and debug commands to troubleshoot WAN connectivity.4—You can verify ISDN with the following commands: show interface show isdn status If show isdn status does not show Layer 1 as ACTIVE and Layer 2 as MULTIPLE_FRAME_ESTABLISHED. CCNA 4. Table 2-1 displays all the options that you can use with the debug ppp command. Module 3 3. you can use the following two commands to view ISDN Layer 2 messages: debug isdn q921 debug isdn q931 You can also use the debug ppp commands previously discussed to identify and troubleshoot Layer 2 issues. . you can verify PPP encapsulation with the show interface command and use the debug ppp command.3.2. and 5 of CCNA 4 in the Cisco Networking Academy curriculum. These commands are outlined in Modules 3.34_1587131749_DAY02. 4. Module 4 4. Table 2-1 PPP Troubleshooting Command Definition debug ppp authentication Displays authentication messages between routers debug ppp packet Displays sent and received PPP packets debug ppp negotiation Displays PPP packets during PPP startup as negotiation occurs debug ppp error Displays PPP protocol errors and statistics debug ppp chap Displays Challenge Handshake Authentication Protocol (CHAP) packets CCNA 4.

exam #640-801). ■ The value 0x4 indicates deleted or that the DLCI was programmed at one point.3. such as obtaining a terminal endpoint identifier (TEI) dynamically Debug isdn q931 Displays call setup information for outgoing and incoming calls Debug dialer packets Displays DDR link connections and interesting traffic that caused the connection Debug dialer events Displays packets sent to the DDR interface isdn call interface interface Forces the local router to dial the remote router Clear isdn bri Clears established connections and resets the interface CCNA 4.7—The command debug frame-relay lmi allows you to view sent and received Local Management Interface (LMI) packets. A type 0 full LMI status message can provide further information with the following hex values: ■ The value 0x0 indicates added/inactive or that the data-link connection identifier (DLCI) is programmed but not usable. but is no longer programmed. Table 2-2 DDR Troubleshooting Command Definition Debug isdn q921 Used to observe signaling events between the router and the ISDN switch.2. Pages 541–546 and 571–574 in the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. The more you see the output and recognize key variables. ■ The value 0x2 indicates added/active or that the DLCI is usable and functioning properly.2.6—The following commands can be used to verify Frame Relay: show interfaces show frame-relay lmi show frame-relay pvc show frame-relay map 5. . Summary Test the commands described today on a router if you have time.34_1587131749_DAY02. the quicker you will be able to answer related questions in the CCNA exam. Second Edition also review WAN troubleshooting and verification.qxd 178 7/28/06 8:59 AM Page 178 31 Days Before Your CCNA Exam 4. Module 5 5.9—The commands in Table 2-2 provide troubleshooting information for dial-on-demand routing (DDR).

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The following sections outline the details from each day that you should feel comfortable with. routers Packets 1 Network Access 2 Data link LLC and MAC. Day 31 The benefits of using a layered model are as follows: ■ Reduces complexity ■ Standardizes interfaces ■ Facilitates modular engineering ■ Ensures interoperable technology ■ Accelerates evolution ■ Simplifies teaching and learning Table 1-1 provides an overview of both the TCP/IP model and the OSI model. SQL Data 3 Transport 4 Transport End-to-end communications. Today you also focus on the common CCNA details that may show up on the exam. hub Bits . exam #640-801).qxd 7/28/06 8:59 AM Page 181 Day 1 Key Points from Each Day for Relaxed Skimming Today you should try to take a timed practice test using either the Cisco Academy practice CCNA or the exam simulation that accompanies the CCNA Flash Cards and Exam Practice Pack (CCNA Self-Study. Something as simple as a default TCP port number or a default administrative distance can quickly highlight the correct answer in the CCNA exam. Second Edition. TCP and UDP Segments 2 Internet 3 Network Path determination. switch Frames 1 Physical Media and signals. Treat today as if you were skimming through a configuration file to find the key details of a router configuration. Table 1-1 The TCP/IP Model Versus the OSI Model TCP/IP Model OSI Model Key Points PDU 4 Application 7 Application User interaction Data 6 Presentation Encryption and compression Data 5 Session Session control.35_1587131749_DAY01. or at least be able to recognize as part of a larger concept. including a short description and the protocol data unit (PDU) for each layer.

all ports are in the blocking or forwarding state until there is a topology change. Table 1-3 Spanning-Tree Port States Port State Description Blocking The port looks only at BPDUs.qxd 182 7/28/06 8:59 AM Page 182 31 Days Before Your CCNA Exam Table 1-2 Application Layer Protocols and Transport Layer Ports Application Layer Protocol Transport Layer Port/Protocol http Port 80 TCP Connection-Oriented FTP Port 21 TCP Connection-Oriented FTP-Data Port 20 TCP Connection-Oriented Telnet Port 23 TCP Connection-Oriented SMTP Port 25 TCP Connection-Oriented DNS Port 53 UDP and TCP TFTP Port 69 UDP Connectionless SNMP Port 161 UDP Connectionless Day 30 Switches perform the following Spanning Tree Protocol (STP) actions to prevent loops in a redundant switched network: ■ Send out bridge protocol data units (BPDUs)—Each switch sends BPDUs that include the bridge ID (BID) containing the bridge priority and MAC address. ■ Cycle ports through the STP states—After the network has converged. Table 1-3 describes the port states. ■ Elect a root bridge—The switch with the lowest bridge priority becomes the root bridge.35_1587131749_DAY01. Forwarding The port learns MAC addresses. Learning The port learns MAC addresses but does not forward data. Listening The port checks for multiple paths to the root bridge and blocks all ports except the port with the lowest cost path to the root bridge. ■ Specify a root port—The port with the best bandwidth connection (lowest cost path) becomes the root or designated port. and processes BPDUs. forwards data. .

Star All devices connected to a hub or switch. Table 1-5 Distance Vector and Link-State Protocols Distance Vector Link-State Routers send periodic updates of the entire routing table to neighbors. Ethernet is a logical bus topology. Ring Hosts connected to other hosts. Routers send link-state advertisements (LSAs) to update other routers. Mesh All devices connected to all other devices. These topologies can describe logical or physical characteristics of a LAN. . FDDI is a logical ring topology. To develop a full loop-free topological database requires more memory in a router. Routers use a metric to determine the cost path for a route and build a routing table. Ethernet is an example of a nondeterministic physical star topology.qxd 7/28/06 8:59 AM Page 183 Day 1 183 Day 29 Table 1-4 describes the different LAN topologies. Hierarchal A pyramid of physical star networks connected to a main proxy.35_1587131749_DAY01. Table 1-4 LAN Topologies Topology Description Bus All devices are connected. Routers use the LSAs to build a full topology of the network. Day 28 Table 1-5 compares the features of distance vector and link-state protocols. Uses CSMA/CD. ■ Cut-through—In cut-through mode. This topology is deterministic. Routers use the Shortest Path First (SPF) algorithm and LSAs to build a shortest path tree as well as a routing table. a switch either sends the frame as soon as it knows the destination MAC address (fast-forward) or the switch reads the first 64 bytes and then sends the frame (fragment-free). Routers flood LSAs only when there is a topology change. Routers see only neighboring routers. Switches can operate in cut-through or store-and-forward modes: ■ Store-and-forward—Store-and-forward mode results in the switch receiving the entire frame before forwarding the information.

OSPF avoids a network of never-ending neighbors with an election. C.35_1587131749_DAY01. uses a distance-vector diffusing update algorithm (DUAL) to recalculate a topology. and E IP addresses. triggered updates. D. D.H. ■ Split horizon does not allow a router to send an update for a route to the router that originally advertised the route.5. ■ If you were to run Open Shortest Path First (OSPF) on a fiber network.0.qxd 184 7/28/06 8:59 AM Page 184 31 Days Before Your CCNA Exam Routers can avoid loops with the following tactics: ■ You can combine route poisoning with the maximum hop count.535 16 Class C 110 192–223 N.H.0. ■ OSPF hello packets typical to link-state protocols go out over the multicast address 224.N. To avoid a single point of failure. This means that each router would be a neighbor to every other router. ■ EIGRP sends hello packets on 224.H. the hellos go out every ten seconds.H About 16 million 8 Class B 10 128–191 N. Routers that are connected on broadcast multiaccess networks such as fiber or Ethernet or nonbroadcast multiaccess networks such as Frame Relay elect a single router called the designated router (DR) to handle updates. If the connection is multiaccess. C.0. Table 1-6 Class A. the packets go out every 30 seconds.0.N.0. ■ The neighboring and topology table allow EIGRP to use DUAL to identify the best route. or feasible successor routes. they also elect a backup designated router (BDR).H. however. If the connection is point-to-point. ■ Enhanced Interior Gateway Routing Protocol (EIGRP) uses a neighboring table in the same way that OSPF uses an adjacency database to maintain information on adjacent routers.0. Backup routes. or the successor route. B.10 to communicate with neighbors. EIGRP. are kept only in the topology table. all routers would technically be connected on the fiber ring to each other. and a holddown timer to prevent routing loops.H 65. and E IP Addresses Class Binary Start 1st Octet Range Network (N) and host (H) Octets Number of Hosts Bits in Network Address Class A 0 1–126* N. Day 27 Table 1-6 explains Class A.H Multicast 28 Class E 1111 240–255 RESEARCH RESEARCH RESEARCH * The Class A address 127.N.H 254 24 Class D 1110 224–239 H.0 is reserved for the loopback. and enter it into the routing table. B. .H.

. the Cisco IOS software searches for a TFTP server to load the configuration file. A remote collision occurs when a frame is too small but does show the same symptoms as a local collision. it first performs a power-on self test (POST). If there is no TFTP server. and TCP functions: ■ Address Resolution Protocol (ARP) finds a MAC address using the IP address. and a three-way handshake and is the Layer 4 connection-oriented protocol. ■ A more concise definition of port number ranges includes well-known ports (0 to 1023). registered ports (1024 to 49151). ■ TCP uses positive acknowledgment. and dynamic ports (49152 to 65535).35_1587131749_DAY01. loads a bootstrap. ■ User Datagram Protocol (UDP) is the Layer 4 connectionless protocol and relies on upper layers for error correction. An example could be a web server that provides HTTP access on port 80 at the same time as Telnet access on port 23. ■ The process in sliding windows where TCP requests that a host resend information is called positive acknowledgement and retransmission (PAR). it loads the configuration file from NVRAM. sliding windows. a TFTP server. If there is no configuration file in NVRAM. IP address assignment occurs at Layer 3. A remote collision is likely the result of a local collision on the other side of a hub or repeater. and initializes the IOS from flash. ■ Port number assignment occurs at Layer 4 of the OSI model. the IOS starts the setup dialog. The location of the IOS can be specified in the configuration register. Day 25 A local collision occurs when a network card notices that the receive (RX) wires and the send (TX) wires are active at the same time. or ROM. Day 26 Consider the following full image name: C2600-is-mz The following defines the image name sections: ■ C2600 = platform = Cisco 2600 series ■ is = feature set = IP Plus ■ mz = image location/compression = RAM/zipped When a Cisco router powers up. ■ A host can provide services simultaneously on two different ports. Once the IOS is loaded. ARP occurs when a host has a destination IP address for a packet but needs to determine the MAC address to send the packet over the LAN. IP.qxd 7/28/06 8:59 AM Page 185 Day 1 185 The following points discuss ARP. and MAC address assignment occurs at Layer 2. The repeater would only regenerate the bad frame and not the simultaneous TX and RX.

You can define a dialer-list on a Cisco router that tells the router what traffic should cause it to bring up a DDR link.0 to 192. it is considered a cyclic redundancy check (CRC) error. Frame Relay switches create a virtual circuit (VC) between communicating hosts that exists only when the frame is being transferred. The Layer 2 network card cannot recognize this type of collision and must rely on the upper layers to request retransmission. ISDN bearer (B) channels carry data at 64 kbps for each channel.255. A binary 1 means ignore and a binary 0 means match in a wildcard mask. A runt is a frame that is below the minimum size of 64 octets.255 ■ Class C 192. Dial-on-demand routing (DDR) interesting traffic is network activity that causes a router to connect to a network.255. The ISDN delta (D) channel is used to set up the call and for signaling.0 to 10.0.35_1587131749_DAY01. and C address ranges for private LANs. Runts are usually made up of collision fragments.0 states that the access control list (ACL) should match the entire host.0. Some common data link layer WAN encapsulation types include the following: ■ Cisco proprietary HDLC ■ PPP ■ LAPB Frame Relay is an example of a Layer 2 WAN connection-oriented packet-switching system where the route is determined by switches and each frame carries an identifier called a data-link connection identifier (DLCI).0. The call with Integrated Services Digital Network (ISDN) is faster than a modem. Day 24 A WAN connection uses a Layer 2 frame to encapsulate data. The VC is identified by the DLCI.0. Day 23 RFC 1918 states that there are reserved Class A. 0. The wildcard mask 0. and the ISDN connection allows for a PPP-encapsulated link. The private ranges are as follows: ■ Class A 10.0 to 172. wildcard masks serve an entirely different function from subnet masks.0. If a frame does not match its own frame check sequence (FCS).31.255 .qxd 186 7/28/06 8:59 AM Page 186 31 Days Before Your CCNA Exam A late collision occurs after the first 64 bits of data have been transmitted for a frame.0.16.255 ■ Class B 172.0 can also be represented by the term any or host in an ACL.168.255. Do not look for a relationship between wildcard masks and subnet masks. A frame that exceeds the maximum legal frame size will cause a network diagnostic tool to report jabber on the connection.255.168.0. B.0.

which connect through horizontal cross-connects (HCCs) to hosts. but you need a router to communicate between VLANs. Table 1-8 Class C Subnet Chart Bits Borrowed 1 2 3 4 5 6 7 8 Slash format /25 /26 /27 /28 /29 /30 /31 /32 Mask 128 192 224 240 248 252 254 255 Bits borrowed 1 2 3 4 5 6 7 8 Total subnets 2* 4 8 16 32 64 N/A N/A Usable subnets* 0* 2* 6* 14* 30* 62* N/A N/A Total hosts 128* 64 32 16 8 4 N/A N/A Usable hosts 126* 62 30 14 6 2 N/A N/A *Stars refer to CCNA 3.35_1587131749_DAY01. . The main distribution facility (MDF) connects through the vertical cross-connects (VCCs) to the intermediate distribution facilities (IDFs). You can divide Layer 2 switches into VLANs to separate networks at Layer 3. Switch ports have only two hosts per collision domain with a source and destination host. Table 1-7 LAN Design by OSI Layer OSI Layer Design Considerations Network (3) Routers commonly forward data based on IP addressing and connect LANs and divide broadcast domains between LANs. The use of hubs instead of switches increases the size of collision domains to all hosts connected and affects bandwidth. Day 22 You can use Table 1-8 to quickly determine the details necessary to subnet a Class C network. Module 1. Routers can also act as firewalls and provide a WAN connection. Data link (2) To microsegment collision domains you should use switches. The /25 subnet is sometimes usable as well as total subnets (all 0s and all 1s) in later versions of the IOS and if you enter the ip subnet zero command.qxd 7/28/06 8:59 AM Page 187 Day 1 187 Table 1-7 outlines LAN design considerations divided by OSI layer. Physical (1) Fiber optic for distances over 100 meters and unshielded twisted pair (UTP) for 100 meters or less.

0. load. Virtual private network (VPN) Provide a private network that exists inside of a public network. Table 1-10 Network Types Network Type Designed To: Wide-area network (WAN) Connect LANs using serial interfaces over a large geographic area to provide remote resources. and delay as a metric.10. Table 1-9 Routing Protocols Protocol Name AD Type Description Routing Information Protocol (RIP) 120 Interior. Supports VLSM. EIGRP 90 Interior. distance vector Multicasts updates every 30 seconds using the address 224. distance vector Broadcasts updates every 30 seconds and uses hop count as the metric with a maximum of 16.0. Supports variable-length subnet mask (VLSM). Clients connect through a secure tunnel to the VPN router at the destination. Day 20 Table 1-10 defines four types of internetworks. distance vector Used to route between autonomous systems. scalable storage for servers over a separate network from the client/server network.9 and includes subnet mask in updates.35_1587131749_DAY01. OSPF 110 Interior. and Internet access. Routing Information Protocol Version 2 (RIPv2) 120 Interior. distance vector Broadcasts updates every 90 seconds and uses bandwidth. a wireless bridge.0. hybrid Uses both link-state and distance vector features and multicasts updates on 224. or optical services. Storage-area network (SAN) Provide high-performance. e-mail.qxd 188 7/28/06 8:59 AM Page 188 31 Days Before Your CCNA Exam Day 21 Table 1-9 charts the routing protocols discussed in the Cisco Networking Academy curriculum. Metropolitan-area network (MAN) Connect LANs in a metropolitan area using private lines. fault-tolerant. Border Gateway Protocol (BGP) 20 Exterior. updates only when there is a change in topology. . Interior Gateway Routing Protocol (IGRP) 100 Interior.0. link-state Nonproprietary protocol.

and Table 1-12 describes PPP session establishment. ■ An ACL should filter specific addresses first and then groups of addresses. ■ A router checks ACL statements in the order in which you create them. and ATM. continues . ■ Place extended ACLs closest to the source. ■ At the end of every ACL. Table 1-11 WAN Connection and Protocol Examples WAN Protocol Network Type Key Points ISDN Circuit-switched BRI has 1 channel for signaling and 2 channels for data. Frame Relay Packet-switched Uses DLCIs to identify circuits and LMI messages to learn about the network. ATM Cell-switched High-bandwidth WAN protocol that uses a 53-byte cell. ■ You can apply to each interface one ACL per protocol per direction. Good for video and streaming applications. it sends an ICMP implicit deny. there is an implicit deny. then LCP opens the connection with a configuration acknowledgment frame. Table 1-11 highlights key points about ISDN. Frame Relay.qxd 7/28/06 8:59 AM Page 189 Day 1 189 Day 19 Remember the following points about ACLs: ■ The way to revise an ACL is to delete and recreate it unless you are using a named ACL and can add statements to the end. ■ When an IP ACL rejects a packet. ■ A router stops checking ACL statements after the first match. Day 18 WAN protocols operate at the physical and data link layers of the OSI seven-layer reference model. ■ Outbound ACLs do not affect traffic originating from the router. ■ Place standard ACLs closest to the destination. Table 1-12 PPP Session Establishment Phase Description Link-establishment phase Each device sends Link Control Protocol (LCP) frames and negotiates LCP options. ■ Do not work with an access list that is applied and active.35_1587131749_DAY01. PRI has 1 signaling channel and 23 data channels.

0.921 link access procedure on the D channel (LAPD) and the Q. The NT2 connects at the T reference to the network termination type 1 (NT1).qxd 190 7/28/06 8:59 AM Page 190 31 Days Before Your CCNA Exam Table 1-12 PPP Session Establishment continued Phase Description Authentication phase (optional) The established link can authenticate using Password Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol (CHAP) and also check link quality. and the NT1 connects at the U reference to the local loop. Day 17 Table 1-13 lists the syntax for different types of routing protocols. Network layer protocol phase PPP devices send Network Control Protocol (NCP) packets to configure network layer protocols and allow Layer 3 transmission. Table 1-13 Routing Protocol Command Syntax Protocol Commands Static ip route destination-network subnet-mask {outgoing-interface | nexthop-address} Default ip route 0.0. so you first connect at the R reference to the terminal adapter (TA) and then to the NT2. including Q. The NT2 connects at the T reference to the NT1. ■ You have a TE2 that is not native ISDN.931 ISDN network layer The following two examples describe ISDN reference points: ■ You have a TE1 that is a native ISDN interface that connects at the S reference to the customer switching network termination type 2 (NT2).0 0. so you may sometimes see an S/T interface. The three categories of ISDN protocols are as follows: ■ E series—Telephone network standards ■ I series—ISDN concepts and terminology ■ Q series—How switching and call setup (signaling) function.35_1587131749_DAY01. and the NT1 connects at the U reference to the local loop.0 {outgoing-interface | next-hop-address} RIP router rip network directly-connected-network IGRP router igrp autonomous-system-number network directly-connected-network OSPF router ospf process-id network network-address wildcard-mask area area-id exit .0. S and T references can be similar.0.

0 Router(config-if)#clock rate 56000 Router(config-if)#no shutdown .1.255.1 255.qxd 7/28/06 8:59 AM Page 191 Day 1 Protocol 191 Commands interface loopback 0 ip address ip-address subnet-mask OSPF simple authentication interface interface ip ospf authentication-key password exit area area-number authentication OSPF authentication with MD5 interface interface ip ospf message-digest-key key-id md5 key area area-number authentication message-digest exit router ospf process id area area-id authentication message-digest EIGRP router eigrp autonomous-system-number network network-number eigrp log-neighbor-changes bandwidth bandwidth no auto-summary Day 16 You use the following command syntax to configure a serial interface.255.35_1587131749_DAY01. You will only use the clock rate command if the interface is data communications equipment (DCE).16. interface type slot/port ip address ip-address netmask clock rate clock-rate no shutdown Example 1-1 Configuring a Serial Interface Router>enable Router#configure terminal Router(config)#interface serial 0/0 Router(config-if)#ip address 172.

255 Router(config)#ip nat pool isp-pool 209.235 netmask 255.1.0 0.0.200.255. Table 1-14 Set the Console and vty Passwords Console Password Configuration VTY Password Configuration line console 0 line vty 0 4 password cisco password cisco login login Table 1-15 NAT and DHCP Configuration Commands Static NAT Configuration DHCP Configuration ip nat inside source static local-IP global-IP ip dhcp pool pool-name interface interface network network-address subnet-mask ip nat outside default-router default-router-address interface interface dns-server dns-server-address ip nat inside domain-name domain-name Example 1-2 NAT Configuration with Overload for One Outside IP Address Router(config)#access-list 1 permit 192.225 209. vty.165.1. NAT.35_1587131749_DAY01.255.200.qxd 192 7/28/06 8:59 AM Page 192 31 Days Before Your CCNA Exam Day 15 Table 1-14 and Table 1-15 recount additional router configurations such as console.224 Router(config)#ip nat inside source list 1 pool isp-pool overload Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside .168.168.0. and DHCP.0 0.0.165.0.255 Router(config)#ip nat inside source list 1 interface serial 0 overload Router(config)#interface serial 0 Router(config-if)#ip nat outside Router(config-if)#interface fa 0/0 Router(config-if)#ip nat inside Example 1-3 NAT Configuration with Overload for a Pool of Outside IP Addresses Router(config)#access-list 1 permit 192.

and VTP configuration commands. modify. due to the wide use of Internet access. and delete VLANs Sends VTP messages out all trunk ports and saves VLAN configuration in the NVRAM. Table 1-16 and Table 1-17 define Virtual Terminal Protocol (VTP) modes and provide static VLAN. However. Client Cannot create. ■ VLAN membership provides security settings assigned for each logical group. modify. Transparent Only forward advertisements Does not modify its VLAN database.qxd 7/28/06 8:59 AM Page 193 Day 1 193 Day 14 Remember the following points about VLANs: ■ VLAN membership is based on job assignment regardless of location (referred to as end-toend). Table 1-16 VTP Switch Modes VTP Mode Capabilities Definition Server Can create. Trunk. trunk.1Q. ■ The two types of frame tagging are Cisco proprietary Inter-Switch Link (ISL) and IEEE 802.1q to connect a Cisco switch to a non-Cisco device. VTP clients process changes and forward messages.35_1587131749_DAY01. and delete VLANs Better for switches that do not have enough memory for large configurations. but forwards received VTP messages. ■ VLAN membership can be configured to follow the users when they change location on the network in an end-to-end network. You would use 802. and VTP Configuration Commands Configuration Type Commands Static VLAN vlan database vlan vlan-number interface interface switchport access vlan vlan-number Trunk switchport trunk encapsulation {isl | dot1q} VTP vlan database vtp v2-mode vtp domain domain vtp {client | server | transparent} vtp password password . geographic VLANs have become more common than end-to-end VLANs. but as previously stated geographic VLANs are more common. Table 1-17 Switch Static VLAN.

The router first looks for the Cisco IOS software in the flash memory. the router first looks for a configuration file in the NVRAM. Once the Cisco IOS software is loaded. A router starts using the following sequence: 1. typically a serial port on a host to a console port on a router or switch Day 12 Bridges and switches divide collision domains and filter at Layer 2. Layer 3 switches and routers filter at Layer 3 of the OSI model and divide broadcast domains. loads a stripped version of the IOS from ROM. 3. Switch to hub Hub to hub Router to router Host/server to host Router to host Straight-through cable Router to switch TIA/EIA-568-A on both ends or TIA/EIA-568-B on both ends. then looks for a TFTP server that could have the IOS. Each port on a bridge or switch is microsegmented into its own collision domain.35_1587131749_DAY01. then looks for a TFTP server that might have the configuration.qxd 194 7/28/06 8:59 AM Page 194 31 Days Before Your CCNA Exam Day 13 Table 1-18 provides a description for different types of UTP networking cable. and lastly. 2. Table 1-18 UTP Cabling for Network Devices Cable Used to Connect Description Crossover cable Switch to switch TIA/EIA-568-A on one end and TIA/EIA-568-B on the other end. Router to hub Host/server to switch Host/server to hub Rollover cable Terminal to console Pins 1–8 reversed on either end. and lastly. Often converted to 9-pin port on a device for serial on one end. if there . if there is no other option. Layer 2 switches can also divide broadcast domains with VLANs. configuration. The router checks the hardware (POST) and loads the bootstrap code from the read-only memory (ROM). but you need a router to communicate between VLANs.

0x___1 0x2101 Boots the first image in flash.0 and later: copy location:URL location:URL The following commands allow you to define how a router will boot: boot system flash IOS-filename boot system tftp IOS-filename tftp-address boot system rom config-register configuration-register-value Table 1-20 deciphers the values in the configuration register. 0x___2 to 0x___F 0x2142. If there are no commands. use the show version command to see if the configuration register value is 0x2142. The specific example 0x2142 ignores any configuration in the NVRAM. . If your router boots to a nonconfigured router (and you saved to startup-config). the system boots the first image in flash. Table 1-19 lists router configuration and backup commands. Table 1-20 Configuration Register Values Register Value Example Description 0x___0 0x2100 System enters ROM monitor mode. 0x2102 would apply the configuration in the NVRAM. outputs a set of questions to the console to ask the user for configuration parameters. 0x2102 Looks in the NVRAM for boot system commands. Table 1-19 Router Configuration and Image Backup Commands Configuration Backup Image Backup copy running-config tftp copy flash tftp copy tftp running-config copy tftp flash xmodem -c image-file-name set tftpdnld Cisco IOS release 12.35_1587131749_DAY01. This setting will boot the limited ROM version on older platforms.qxd 7/28/06 8:59 AM Page 195 Day 1 195 is no configuration. Use b to boot the system.

35_1587131749_DAY01.qxd 196 7/28/06 8:59 AM Page 196 31 Days Before Your CCNA Exam Day 11 Table 1-21 and Table 1-22 cover the keystrokes used in the Cisco IOS software as well as editing commands and initial router commands. Table 1-21 Cisco IOS Editing Keys and Commands Command/Keystroke Definition Tab Automatically complete a command Ctrl-P or Up Arrow Repeat previously typed commands Ctrl-A Move to the beginning of a command line Esc-B Move back one word Ctrl-B or Left Arrow Move back one character Ctrl-E Move to the end of the command line Ctrl-F or Right Arrow Move forward one character Esc-F Move forward one word Ctrl-Z Exit configuration mode show history Display the command buffer terminal history size number Set the history buffer size terminal no editing Turn off advanced editing terminal editing Enable advanced editing Table 1-22 Common Initial Router Commands and Switch Commands Router Commands Switch Commands enable enable configure terminal configure terminal hostname hostname hostname hostname banner motd copy running-config startup-config enable secret password copy running-config startup-config .

DDR. Table 1-24 WAN Configuration Commands Protocol Basic Commands PPP encapsulation ppp compress {predictor | stac} ppp quality {1 to 100 as a percentage} ppp multilink username name password secret-password encapsulation ppp ppp authentication {chap | chap pap | pap chap | pap} ppp pap sent-username username password password continues . ISDN. and Frame Relay.qxd 7/28/06 8:59 AM Page 197 Day 1 197 Day 10 Table 1-23 provides the commands needed to configure different ACLs.35_1587131749_DAY01. Table 1-23 Access List Commands ACL Type ACL Commands Standard access-list ACL-number {deny | permit} source-address wildcard ip access-group ACL-number {in | out} Extended access-list ACL-number {deny | permit} protocol source wildcard-mask destination wildcard-mask operator port ip access-group ACL-number {in | out} Restrict VTY access-list ACL-number {deny | permit} source-address wildcard-mask ip access-class ACL-number {in | out} Named ACL access-list {extended | standard} name {deny | permit} protocol source wildcard destination wildcard-mask operator port ip access-group ACL-number {in | out} You can use numbers from the following ranges to identify a numbered access list: ■ Standard IP ACL—Numbers 1–99 or 1300–1999 ■ Extended IP—Numbers 100–199 or 2000–2699 ■ AppleTalk—Numbers 600–699 Day 9 Table 1-24 lists the commands that you would use for PPP.

qxd 198 7/28/06 8:59 AM Page 198 31 Days Before Your CCNA Exam Table 1-24 WAN Configuration Commands Protocol Basic Commands ISDN BRI isdn switch-type switch-type continued isdn spid{number} spid-number local-dial-number encapsulation ppp ISDN PRI controller t1 framing {sf | esf} linecode {ami | b8zs | hdb3} pri-group timeslots range interface serial {slot/port: | unit:} {23 | 15} isdn switch-type switch-type controller e1 framing {crc4 | no-crc4} linecode {ami | b8zs | hdb3} pri-group timeslots range interface serial {slot/port: | unit:} {23 | 15} isdn switch-type switch-type DDR.35_1587131749_DAY01. legacy dialer-list number protocol protocol {permit | deny | list [access-list-number]} interface interface dialer-group number dialer idle-timeout seconds-after-last-traffic dialer map ip next-hop name next-hop-hostname dial-number DDR. dialer profiles dialer-list number protocol protocol {permit | deny | list [access-list-number]} interface dialer virtual-interface-number dialer-group number dialer remote name next-hop-hostname dialer string dial-number dialer-pool number dialer idle-timeout seconds-after-last-traffic dialer pool-member number priority priority Frame Relay (no LMI) encapsulation frame-relay {cisco | ietf} frame-relay map protocol protocol-address dlci broadcast Frame Relay encapsulation frame-relay {cisco | ietf} frame-relay lmi-type {ansi | cisco | q933a} interface serial subinterface-number {point-to-point | multipoint} frame-relay interface-dlci DLCI-number .

To see information about neighboring devices. Table 1-25 OSI Model Troubleshooting Layer Common Issues Layers 7–4 Ping works. Telnet tests all seven layers of the OSI model. use the command show cdp neighbors. DTE and DCE cable problems or transceiver issues. Ping tests Layer 3.qxd 7/28/06 8:59 AM Page 199 Day 1 199 Day 8 Table 1-25 pinpoints the common issues you encounter on a network in relation to the OSI sevenlayer model. Day 7 Make sure that you are familiar with the following commands for LAN and VLAN troubleshooting: cdp run show debugging no cdp run debug cdp adjacency no cdp enable debug cdp events clear cdp counters debug cdp ip cdp enable debug cdp packets show cdp traffic cdp timer show cdp cdp holdtime show cdp neighbors show debug show cdp neighbors detail show vlan clear cdp table The command show cdp does not show information about neighboring devices. . LED indicators and power LED–related issues. It tells you about the configuration of CDP on the device you are using. Layer 2 Improper or missing configurations for clock rate and encapsulation. Layer 3 IP addressing and routing protocol configuration issues. Layer 1 Incorrect cables.35_1587131749_DAY01. but Telnet does not work.

you can type that portion of the command followed by a question mark (?) to view the options for that command.0/0 eBGP.qxd 200 7/28/06 8:59 AM Page 200 31 Days Before Your CCNA Exam Day 6 Table 1-26 specifies the commands that can aid you while troubleshooting a routing protocol. If part of the command was understood.35_1587131749_DAY01. 200 debug ip ospf events debug ip ospf packet Days 5 and 4 Be sure to remember the commands. 20 show ip rip database EIGRP (internal). The telnet command can . 115 no debug all RIP. Table 1-26 Routing Protocol Troubleshooting Commands Default Administrative Distances debug ip igrp events Directly connected. 5 ip route 0. and key combinations that you can use with the Cisco IOS software while troubleshooting a network. 0 debug ip igrp transactions Static. 170 show ip ospf neighbor iBGP. 1 ip default-network EIGRP summary route. 90 show ip interface brief IGRP. 100 show running-config OSPF. 110 undebug all IS-IS.0. 120 show ip eigrp neighbors EIGRP (external).0. show ip route show ip protocols show controllers debug all terminal monitor traceroute ping You can look for the carat symbol (^) to determine the portion of the command that the router did not understand. concepts.

All of the information in this book.35_1587131749_DAY01. then x. and the Academy Curriculum can be whittled down to just one four-letter word on your resume: CCNA. You can look at all sessions with the command show sessions and use disconnect to disconnect a session and resume to resume a session. and extended access lists should be placed as close to the source of the traffic you want to filter. while show commands provide a specific snapshot for a point in time on a network. Treat each detail like a familiar old friend and not a hard. Good luck on the test. ISDN. What is possibly the most important factor for success on the exam is your attitude. cold obstacle. I do realize that this last day is an abbreviation of my abbreviation of the Academy curriculum. Your passion for this subject will come through on test day just as clearly as it will come through in a job interview or planning meeting. . Read with a smile.qxd 7/28/06 8:59 AM Page 201 Day 1 201 be suspended with the keystroke Ctrl-Shift-6. Day 2 The following commands allow you to troubleshoot WAN protocols such as PPP. Summary All the topics discussed today should be floating around in your head within reach for test day. the Cisco IOS software. and Frame Relay: debug ppp authentication debug isdn q931 debug ppp packet debug dialer packets debug ppp negotiation debug dialer events debug ppp error isdn call interface interface debug ppp chap clear isdn bri show isdn status debug frame-relay lmi debug isdn q921 Remember that debug commands are an ongoing presentation of changes on a network. Day 3 Tahe following show commands can help you troubleshoot an access list: show access-lists show ip interface show running-config Standard access lists should be placed as close to the destination of the traffic you want to filter. Use debug commands only when you are troubleshooting.

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qxd 7/28/06 8:59 AM Page 203 Part V Exam Day and Post-Exam Information Exam Day: Becoming a CCNA Post-Exam: After the CCNA Exam .36_1587131749_Pt5.

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The minimum score required to pass is around 800 (the minimum score listed on my last exam report was 849). The proctor will give you a certified score report with the following important information: ■ Your score based on a scale of 300 to 1000 points. Use the following information to focus on the details specific to the day of your CCNA exam. and technology sections of the exam. It is best to bring only what you will need. exam center phone number. What You Need for the Exam Write the exam location. Cisco. The report will also include your percentage in the planning and design.qxd 7/28/06 8:59 AM Page 205 Exam Day Becoming a CCNA Today is your opportunity to prove that you know how to describe. and troubleshoot a network. implement.com explains that the scoring scale . plan. implementation and operation. Ninety minutes and 65 questions stand between you and your CCNA certification. Do not take these out of the room. exam time.37_1587131749_ExamDay. ■ The test proctor will give you a sheet for scratch paper or a dry erase pad. or military identification. troubleshooting. you will see an immediate electronic response as to whether you passed or failed. passport. ■ The testing center will store any personal items while you take the exam. and the proctor’s name in the lines that follow: Location: Date: Exam Time (arrive early): Exam Center Phone Number: Proctor’s Name: Remember the following items on Exam Day: ■ You must have two forms of ID that include a photo and signature such as a driver’s license. ■ The test proctor will take you through the agreement and set up your testing station after you have signed the agreement. ■ You will be monitored during the entire exam. date. What You Should Receive After Completion When you complete the exam.

If you know the details of the curriculum and the details of the exam process. so answer each question confidently and keep an eye on the timer. ■ Identification information that you will need to track your certification. Do not lose your certified examination score report.qxd 206 7/28/06 8:59 AM Page 206 31 Days Before Your CCNA Exam could change without notice. Bring earplugs in the off chance that your testing neighbor has a bad cough or any loud nervous habits.37_1587131749_ExamDay. but the scoring has remained the same for the last three versions of the CCNA. Do not let an extremely difficult or specific question impede your progress. Summary Your state of mind is a key factor in your success on the CCNA exam. . You cannot return to questions on the exam that you have already answered. you can begin the exam with confidence and focus. Arrive early to the exam.

It won’t happen all at once.38_1587131749_PostExam. Receiving Your Certificate If you passed the exam. Determining Career Options After passing the CCNA exam. Matthew Moran provides the following advice for adding certifications to a resume in his book. The following sections discuss your options after test day. A master’s degree might be the exception to this rule. If you can master those skills at your current position. or some other advanced degree. Many network engineers have avoided the CCNA exam for years. You will need your examination score report to log in to the certification tracking system and set up a login to check your certification status. It is presumptuous to pretend that your latest certification is the equivalent to someone who has spent 4–7 years pursuing a Ph. you have to open a case in the certificate online support located at the following web address: http://ciscocert. You must build your career piece by piece. you will receive your official CCNA certificate and wallet card about six weeks (eight weeks internationally) after exam day. The IT Career Builder’s Toolkit (Cisco Press. Instead. you should be satisfied. place your certifications or degrees in a section titled Education and Certifications. be sure to add your CCNA certification to your resume. 2005. To keep your certificate valid.custhelp. while simultaneously building your network of contacts that lead to your dream position. .qxd 7/28/06 9:00 AM Page 207 Post-Exam Information After the CCNA The accomplishment of signing up for and actually taking the CCNA exam is no small feat.com/ When you receive your certificate. You never know when an employer or academic institution could request a copy. Moran also discusses good strategies for breaking into the IT industry once you have earned your CCNA: The most important factor is that you are moving toward a career goal. You might not get the title or job you want right out of school. ISBN: 1587131560): I don’t believe you should place your certifications after your name. A certificate hanging on a wall is much harder to lose than a certificate in a filing cabinet or random folder.D. Your CCNA is valid for three years. you must pass the CCNA again or pass another Cisco exam in a path to a professional level certification before the end of the three year period. If you do not receive your certificate. Your certificate will be mailed to the address you provided when you registered for the exam. you may want to frame it and put it on a wall.

If You Failed the Exam If you fail your first attempt at the CCNA. Two common professional certifications are the Cisco Certified Network Professional (CCNP) and the Cisco Certified Security Professional (CCSP). Examining Certification Options Although passing the CCNA exam is not an easy task. and employed for a lifetime.38_1587131749_PostExam. As a Cisco Networking Academy alumnus. and Packet Tracer provides an excellent simulator for most CCNA configurations. . continued network study and testing should feel more familiar.qxd 208 7/28/06 9:00 AM Page 208 31 Days Before Your CCNA Exam Moran also outlines in his book that certifications such as the CCNA are part of an overall professional skill-set that you must continually enhance in order to further your IT career. Stay motivated and sign up to take the exam again within a 30-day period of your first attempt. If you are familiar with the general concepts. but with a CCNA under your belt. you have access to the curriculum. remember to marvel at the innovation and creativity behind each concept you learn. It is unlikely that you will be hired simply because you have a CCNA. When you log in to the online certification tracking tool (use the exam report to do this). Consider your first attempt as a formal practice exam and as excellent preparation for passing the second attempt. Your CCNA certificate proves that you are disciplined enough to commit to a rigorous course of study and follow through with your professional goals. you have to wait at least five calendar days after the day of the exam to retest. Even though you have listed the CCNA on your resume. Summary Whether you display your certificate and update your resume or prepare to conquer the test on your second attempt. it is important to highlight your networking skills that pertain to the CCNA in your job and skills descriptions on your resume. The ability of our society to continually improve communication will keep you learning. focus on taking practice exams and memorizing the small details that make the exam so difficult. This link provides specific information about professional-level certifications that you can work toward with your CCNA as the base. it is the starting point for more advanced Cisco certifications. and finding a study group or online community can help you with those difficult topics. discovering. be sure to view the certification progress link. but it will place you ahead of other candidates. Both of these certifications require you to pass multiple tests. The score report outlines your weaknesses.

38_1587131749_PostExam.qxd 7/28/06 9:00 AM Page 209 Post-Exam Information Your Notes 209 .

38_1587131749_PostExam.qxd 7/28/06 9:00 AM Page 210 .

6 protocols. 73 extended. 5 OSI layers. 136 finding. 167-168 VLSMs. 73 anemd. 40 named. 197 overview. 71 binary-to-decimal conversion. 91 advanced certifications. 107 NAT. 207 Address Resolution Protocol (ARP). 6 port associations. 60 MAC. 19 analog dial-up WAN service. 9 VPNs. determining. 74 verifying.39_1587131749_Index. 6. 40 name associations. 175 standard. 73 IP address matching. 143. router commands. 39 placement. 52 addresses broadcast.qxd 7/28/06 9:00 AM Page 211 Index SYMBOLS $ (dollar signs). restricting. 208 advertisement requests. 142 number specifications. 110 IP allocation. restricting. 29. 142 filtering options. 27 obtaining. 51 static configuration. 27. 27. 4 protocols. 60 private. 58 classes. 30 A access control lists. 6 hosts. 30 matching. 73 ACLs (access control lists). 58 subnetting. 74 wildcard masks. 79 AND operator. 57 broadcast. 71 American Registry of Internet Numbers (ARIN). 74 traffic. 15 clearing/viewing. 17 adding CCNA to resumes. 73 active hubs. 133 ^ (caret symbols). 91 adaptability of LANs. 9 . 73 configuring. 29 classes (LANs). 74. 57. 29. 143 VTY lines. 197 creating. 58 reserved network. 141. 182 TCP/IP. controlling. 52-53 DHCP. 53 octets. 189 packets. 61-62 network addresses. 141 numbered. 57 private. 58-61 troubleshooting. 40. 74 applying. 117 allocating IP addresses. 73 user protection. 143 access-list command. 143 access-class command. 175 vty access. 133 128-bit IP version 6 (IPv6). 69 vty. 186 administrative distance (AD). 30 private. 40. 30 Internet. 142 guidelines. 133 ? (question marks). obtaining. 184 finding. 19. 74. 60 application layer OSI. See ACLs layers. 28 IPv6. 40. line scrolling. 49 AD (administrative distance). 54 adaptive cut-through mode (switches). 29 determining. 137 network. command errors. 19.

207 caret symbols (^). 160 enabled devices. 111 LANs. sending. 97 interfaces. 208 CDP (Cisco Discovery Protocol). 208 CCSP (Cisco Certified Security Professional). 133 Carrier Sense Multiple Access/Collision Detection (CSMA/CD). 145-146 avoiding loops. 73 ARIN (American Registry of Internet Numbers). 58 DHCP. 121 bridges IDs. 30. 49 C cable modem WAN service. 6. improving. 205 . 95 PPP. 27 Boot ROM. 111 bits per second (bps). 11 broadcasts addresses. 17. 65 BPDUs. 194 WANs.39_1587131749_Index. 85 BGP (Border Gateway Protocol). 195 switches. 43 central processing unit (CPU). clearing. 137-138 bandwidth EIGRP. 122 UTP. 43 CAM (content addressable memory). 29. 122 fiber-optic. 36 boot system commands. 121 blocking port state. 122 types. 20. 11 bps (bits per second). 51 career options. 159 activity. 80 cabling. 124 ScTP. viewing. 17 burned-in addresses (BIA). 207 certified score reports. 52 AS (autonomous system) numbers. 159 CDPv2 (CDP version 2). 65 BIA addresses. 94 LANs. 19 ATM WAN service. 39 Catalyst 1900 switch configuration. 127 booting routers. 35. 160 device details. 17 Layer 2. 17 root. 80 authentication OSPF. 127-128. 57 bindings (DHCP). See MAC addresses BIDs (bridge IDs). 11 LANs. See MAC addresses buses. 129 routers.qxd 212 7/28/06 9:00 AM Page 212 applying ACLs applying ACLs. 27. 159 central office (CO). 160 version 2. 11 binary-to-decimal conversions. 49-51 network functionality. 71 Border Gateway Protocol (BGP). 159 starting. 159 SNAP. 159 turning off. 50 coaxial. monitoring. 122 legacy 10 Mbps Ethernet standards. 12 Boolean logic. 159 cdp run command. 122-123. 159 cdp enable command. 159 information. 20. 122 STP. 195 BOOTP (Bootstrap Protocol). 35 certificates. 184 B backing up IOS images. 121-122 BECN (Backward ECN). 136 CCNP (Cisco Certified Network Professional). 136 Catalyst 2950 switch configuration. 19 ARP (Address Resolution Protocol). command errors. 15.

133 clock rate. 52-53 IP addresses. 164-165 troubleshooting. verifying. 178 LANs. 186 local. 159 clear isdn bri command. 177 editing. 165 IGRP. 199-201 no cdp enable. 133 show. 90 ip default-network. 136 switches. 196 routers. 111 ip route 0. 160 cdp enable. 134 ip access-group. troubleshooting. 29. 57. 187 classes address. 91 ping ICMP messages. 165 RIP verification. 134 213 . troubleshooting. 100. 36. 175 show cdp neighbors. 208 Certified Security Professional (CCSP). 60 passive-interface. 168 history. 185 networks. 32 Layer 3 connectivity. 178 EIGRP. 163-165 OSPF. 143 access-list. 43 coaxial cables. 127 CDP activity monitoring. 36. 191 command history. 172 debug frame-relay lmi. 160 no cdp run. 133 clock rate command. 133 extended ping. 98. 55 class boundaries. 100.qxd 7/28/06 9:00 AM Page 213 commands CHAP (Challenge Handshake Authentication Protocol). 175 EIGRP verification. 134 errors. 178 debug ip dhcp server events. 155. 165 IGRP verification. 133 debug DDR. 17. 73 ip classless. 178 clearing MAC addresses. 159 cdp run. 184 clear cdp counters command. 106-107. 111 debug ppp interface. 99 commands access-class. 159 show cdp neighbors detail. 160 no debug all. 159 ACLs. 82 IOS. 159 Cisco IOS editing. troubleshooting.39_1587131749_Index. 195 configuration/backup. 39. 165 RIP. 164 no ip subnet-zero. 134 configure terminal. 130 show history. 163 isdn call interface. 196 viewing. 159-160 HDLC encapsulation.0. 51 remote. 99 client/server models. 160 show controllers. 73 ACLs. 178 clock. 164-165 show access-lists. 51 clock command. 82 Cisco Certified Network Professional (CCNP). 197 boot system. troubleshooting. 163-165 OSPF.0/0. 135 CLI (command-line interface). 159 clear isdn bri. ignoring. 191 CO (central office). 196 clear cdp counters. 172 show flash. configuring. 195 initial. 36. 90 Class C Subnet chart. 122 collisions domains. 52 late.0. 171 routers booting. 159-160 Discovery Protocol. 208 devices. 163 ip helper-address. 37 Three-Layer Hierarchical Model. 185 command-line interface (CLI).

45. 36 show vlan. 94 deleting. 108 EIGRP. 96-98 Frame Relay. 7 WAN data. 128 restoring. 197 extended. 130 communication CSMA/CD. 108 static routes. 133 configuring ACLs. 163 show ip route. 102 serial. 111 show ip interface. 192 Frame Relay PVC. 171 vty. 126 configuration registers customizing. 192 restoring. 99 loopbacks. 100-102 VLSMs. 147-149 DHCP. 105-106 port security. 90. 99 nodes. 115 switches. 163. 128 values. 134 tftpdnld. 137 RIP. 93 routers commands. 43. 197-199 xmodem. 142 named. 167 terminal editing. 130 traceroute. 195 configure terminal command. 163. 172 terminal no editing. 142 DDR. 101 Ethernet. 3 serial WANs. 110 OSPF. 192 routes default. 175 show ip protocols. 44 components LANs. 94. 101 descriptions. 114-115 VLANs. 90 static. 15 routers. 91 subinterfaces. 146-147 load balancing paths. 93-95 passwords. 175 show version.qxd 214 7/28/06 9:00 AM Page 214 commands show interface. 150 . 172 show ip rip database. 81 service providers. 149-150 IGRP. 39 LANs. 51 TCP. 134 terminal monitor. 35 configuration files copying. 135. 135 NAT. 192 DHCP. 93 ISDN. 177 show ip dhcp binding. 191 static MAC addresses. 195 console. 177 show running config. 171-172 troubleshooting. 69 login banners. 92 interfaces bandwidth. 78 switches. 199-201 WANs. 141 commands. 172 show isdn status. 101-102 IP addressing conventions. 192 verifying. 127 storing. 107 NAT overload. 134 terminal history size. 110 dynamic NAT. 137 static NAT. 172 undebug all. 111 show ip dhcp server statistics. 164 vlan database. 91 local intranets. 115. 109. 105 initial configuration example. 196 telnet. 149 hostnames. 52 networks.39_1587131749_Index. 89 serial interfaces.

95 debug commands DDR. 164-165 troubleshooting. 145 connections Frame Relay networks. 35-36 trunk. 43 HSSI. 172 debug frame-relay lmi command. 128 core layer (three-layer hierarchical model). 125-126 trunk. troubleshooting. 43 CPU (central processing unit). 77 speeds. 11 routers. 9 CPE (customer premises equipment). 192 passwords. 85 switches. 193 WANs commands. 43 switched circuits. 128 routers boot process. 27 default administrative distances. 135 customizing. troubleshooting. 4 WANs. 193 VLANs. 85 LANs. 43 physical. 39-40 data link layer OSI. 39 crossover cables. 147-149 troubleshooting. 116 cyclic redundancy check (CRC). 123 crosstalk. 16 Frame Relay. 122-123 CSMA/CD (Carrier Sense Multiple Access/Collision Detection). 163-165 OSPF. 44. 105 TIA/EIA-232 port connections. 136 Catalyst 2950. 115 verifying. 178 dead intervals (OSPF). 178 EIGRP. 114 static commands. 113 global configuration mode. 165 RIP. 51 control messages. 43 DDR (dial-on-demand routing). 43 demarcation points. 39 D data field (IP packets). 114 VTP. 114-115 vlan database command. 125-126 VLANs. 78 data terminal equipment (DTE). 43 customizing configuration registers. 117 trunking. 157 redundant. 164 . 74 215 convergence networks. 32 controlling traffic. 44. 16 Layer 3. 39 customer premises equipment (CPE). 43 digital. 178 configuring.39_1587131749_Index. 161 WANs.qxd 7/28/06 9:00 AM Page 215 default administrative distances switches Catalyst 1900. 117. 136 clearing. 178 debug ip dhcp server events command. 45. 79 types. 193 subinterfaces. 128 switch configurations. 11 routers. 31 data flow. 171 Layer 4. 81 cabling. 43 branch networks. 111 debug ppp command. 35 CRC (cyclic redundancy check). 177 decimal and binary conversions. 37 content addressable memory (CAM). 77 console configuring. 17. 165 IGRP. 19 copying configuration files. troubleshooting. 73 VTY lines with ACLs. 197-199 PPP encapsulation. 45 equipment.

30. 54 Ethernet frames. 74. 111 dial-on-demand routing. 133 DoS (denial-of-service) attacks. 43 DUAL (diffusing update algorithm). 67 bandwidth.qxd 216 7/28/06 9:00 AM Page 216 default routes default routes. 71 message counts. See EIGRP enterprise servers (LANs). 145-146 WANs. 50 Layer 2 technology. 90 deleting interface configurations. 15. See DDR dialer profiles. 101-102 LANs. 24 troubleshooting. 24. 148-149 diffusing update algorithm (DUAL). 168 stars. 115 demarcation points (WANs). 205 excluding addresses (DHCP). 186 encrypting passwords. 108 E editing keys/commands. 110 EXEC mode routers. 40. 25 features. 111 configuring. 53 internetworks. 16. 106 Enhanced Interior Gateway Routing Protocol.39_1587131749_Index. line scrolling. 111 broadcasts. 24 route summaries. 33 designs LANs. 9 WANs. 22 configuring. 69 . 110. 92 VLANs. 70 IP address allocation. 49 exterior routes (IGRP). 43 denial-of-service (DoS) attacks. 90 propagating with OSPF. 64. 96 DUAL algorithm. 49 DHCP (Dynamic Host Configuration Protocol). 66 multiprotocol support. 110 bindings. 22 extranet VPNs. 24-25 Dynamic Host Configuration Protocol. 20. 17 exam day. 9 DNS (Domain Name System). 145 SNMP. 5 networks. 31 devices Cisco. excluding. 6 dollar signs ($). 64 advanced features. 111 starting/stopping. 81 destination address field (IP packets). 111 processes. 80 DTE (data terminal equipment). 45 digital subscribe line (DSL). 134 EIGRP (Enhanced Interior Gateway Routing Protocol). 16 interfaces. 98 enabling PPP. 70 addresses. 183 distribution layer (three-layer hierarchical model). 159-160 network. 101 static routes. 97-98 topology tables. 20. 33 DSL (digital subscriber line). 112 encapsulation PPP. 192 host IP addresses. 24-25 digital connections (WANs). 165 verifying. 96 verifying. 77 distance vector protocols. See DHCP dynamic NAT. 97 configuring. 77 DSL WAN service. 142 ping command. 187 networks. 23 packets. 133 extending ACLs.

81 High-Speed Serial Interface (HSSI). 85 forwarding DHCP broadcasts. 85. 5 fiber-optic cables. 85 verifying. 78 header checksum field (IP packets). 186 configuring. 83 Layer 2 frames. 11 port state. 39 WANs. 16 forwarding. 126 filtering ACL options. 78 history of commands. 130 flat WAN topology. 52 flags field (IP packets). 17 runts.qxd 7/28/06 9:00 AM Page 217 hubs F failing the exam. 54 HDLC frames. 78 hubs. 123 FDDI (Fiber Distributed Data Interface). 44-46. 85 inverse ARP messages. 53 HSSI (High-Speed Serial Interface). 54 host-to-network layer. 121 global configuration mode (VLANs). 108 hosts full-duplex bandwidth. 128 restoring. 49 networks. 6-7 Forward ECN (FECN). 111 frames. 44 full-duplex bandwidth. 43. 85 FEXT (far-end crosstalk). 5 TCP segments. 17 interfaces. 122 fields EIGRP topology table. 83 Layer 2. 105 testing. 52 sessions. 8 files (configuration) copying. obtaining.39_1587131749_Index. 31 ISDN frames. 23 hierarchy defined. 5 feasible distance field (EIGRP topology table). 31 hello intervals. 208 far-end crosstalk (FEXT). 85 WANs. 12 fragment offset field (IP packets). 78 ISDN. 53 LANs. 31 flash. 142 traffic. 99 IP addresses. 178 217 virtual circuits. 33 traffic. 123 Fiber Distributed Data Interface (FDDI). 30. 35. 149-150 connections. 86 LAN connections. 11 HDLC. 16 IP packets. 85 LMIs. 95 hello packets. 24 feasible successor routes. 134 horizontal cross-connects (HCCs). 79. 17 G-H Gbps (gigabits per second). 85 switches. 80 frames Ethernet. 31 Frame Relay. 43. 24 Ethernet frames. 81 flow control. 7 simultaneous services. 15 high-bandwidth low latency WANs. 49 . 114 HCCs (horizontal cross-connects). 127 storing. 24 FECN (Forward ECN). 6 hostnames (routers) configuring. 5 processing.

71-72. 102 VLSMs. 128 IOS images. 91 serial. 92 exterior routes. 28 layer (TCP/IP). 113 interfaces configuration mode (routers). 111 IP packets. obtaining. 40 name associations. 28 IPv6. 22 interior routes. 58 subnetting. 60 ip classless command. 129-130 IOS naming conventions. 163 . 31 IDF (intermediate distribution facility). 71 binary-to-decimal conversion. 129 ip access-group command. 167-168 VLSMs. See ISDN Inter-Switch Link (ISL). 82 ip default-network command. 163 images IOS. 99 loopbacks. 113 IFS (IOS File System). 54 Internet Control Message Protocol (ICMP). 57.qxd 218 7/28/06 9:00 AM Page 218 ICMP (Internet Control Message Protocol) I ICMP (Internet Control Message Protocol). 84 OSPF costs. See IGRP interior routes (IGRP). 6 hosts. 29. 35. 22 troubleshooting. 196 initial router configuration example. 86 IOS File System (IFS). 101 Ethernet. 101-102 IP addressing conventions. 22 routing updates. 100. 57 broadcast. 20. 69 inverse ARP messages. 70 WANs. 21 system routes. 80 intranet VPNs. 107 NAT. 94 deleting.0. 53 octets. 94. 64 configuring. 61-62 network addresses.0. 184 finding. 113 Integrated Service Digital Network. 102 serial. 163 IP header length field (IP packets). 6 internetworks DHCP. 30 matching. 57 private. 32 identification field (IP packets). 70-71 dividing switches into VLANs. 163-165 verifying. 188 VLANs. 93 information field (EIGRP topology table). determining. 70 types.0/0 command. 135 Institute of Electrical and Electronics Engineers (IEEE). 31 ip helper-address command. 30 Internet. 73 IP addresses allocating. 185 initial router commands. 191 Interior Gateway Routing Protocol. 29. 32 IP addresses. 100 configuring bandwidth. 54 IEEE (Institute of Electrical and Electronics Engineers). 129-130 names. 95 routing. 27 obtaining. 31 ip route 0. 22 intermediate distribution facility (IDF). 24 ISDN. 58 classes. 128 IGRP (Interior Gateway Routing Protocol). 101 descriptions. 58-60 troubleshooting. 58 reserved network.39_1587131749_Index. 70 NAT/PAT. 90 IP Control Protocol (IPCP).

124 types. 51-52 noise. 207 J-K-L kbps (kilobits per second). 190 reference points. 51 networks. 16. 147 frame fields. 43 late collisions. 51 wireless. analyzing. 30 ISDN (Integrated Service Digital Network). 122-123 OSI Layer 1 schemes. 190 verifying. 17 cabling legacy 10 Mbps Ethernet standards. 17. 52-53 ARP. 54 Ethernet. 54 network devices. 85 switches. 177 WANs. 51 topologies. 199-201 virtual circuits. 54 full-duplex bandwidth. 77 BRI. 54 segmenting with routers.39_1587131749_Index. 53. 52 IP addresses. 55 peer-to-peer networks. 54 address classes. 159-161 commands. 83 interfaces. 121-122 bridges. 50 LAPF (Link Access Procedure for Frame Relay). 187 enterprise servers. 50-51 broadcasts. 146 PRI E1. 83-84. 55 OSI Layer 3 schemes. 54 scalability. 146 configuring. 123 Cisco Three-Layer Hierarchical Model. 121 keys. 54 gateways to WANs. filtering. 49 NICs. identifying. 17. 17 Layer 2 frames. 134 LANs (local area networks) adaptability. 53 local machines. 50 requirements. 54 private addresses. 51 performance. 83 PRI. 17 functionality. 50. 55 client/server models. 53 ports. 15 connections. 178 ISL (Inter-Switch Link). 51 collisions. 186 repeaters. 35. 78 hosts. 5 . 53 latency. 50 219 expectations. 122 switches content addressable memory. 54 OSI Layer 2 schemes. 52 bandwidth. regulating.qxd 7/28/06 9:00 AM Page 219 Layer 2 frames IPCP (IP Control Protocol). 54 designs. 54 routers. 69 manageability. 52 troubleshooting CDP. 79 isdn call interface command. 52 components. 51-52 communication. 113 The IT Career Builder’s Toolkit. 84 out-of-band signaling. 17 local intranets. 186 latency LANs. 83. 122 UTP. 52 physical layers. 82 IPv6 (128-bit IP version 6). 39. 17 Layer 2 broadcasts. 45. 16 data. 85 last mile. 51 host traffic. 16 Frame Relay. 63 signals. 183 traffic. 147 protocols. 51 Layer 2 broadcasts.

36 MANs (metropolitan-area networks). 9 transport. 121 MDF (main distribution facility). 155. 12 leased line WAN service. 15 messages control. 155 Layer 4 connectivity. 181 OSI. 6 network access. 181 monitoring CDP activity. See MAC addresses megabits per second (Mbps). 160 . 107 loopback interfaces. 53 logical topologies. 182 routers. 167 troubleshooting. 6 port associations. 137 main distribution facility (MDF). 199 TCP/IP. 22 vector. 37 Link Access Procedure for Frame Relay (LAPF). 155 troubleshooting. 12 M MAC (Media Access Control) addresses. compared. 54 management ports. 44 models. 44 TCP/IP. 102 loops avoiding. 35 routers. 69 local loops. 65 distance vector protocols. 85 link-state protocols. 49 mesh networks. 155-157 overview. 86 VTP. 80 LED lights (routers). 9 internet. 6-8 three-layer hierarchical model. 157 layers data link. 70 memory content addressable. 64 updates. 184 redundancy. 171 Layer 4 connectivity. 28 application. 15 clearing/viewing. 116 metropolitan-area networks (MANs). viewing. 183 Linksys routers. 121 membership (VLANs). 51 static configuration. 43 local machines (LANs). 82 learning port state. 6 transport. 85 Link Control Protocol (LCP). 36 mesh. 21 listening port state. 5-6. 136 finding. 181 OSI Layer 3 connectivity. 12 LMIs (link management identifiers). 54 Media Access Control. 69 masks (VLSMs). 78 LCP (Link Control Protocol). 51 nonvolatile random-access (NVRAM). 54 WANs. 69 microsegmentation. 32 WANs. 15 login banners. 91 local area networks. 85 load balancing paths/routers. 20.qxd 220 7/28/06 9:00 AM Page 220 Layer 3 connectivity Layer 3 connectivity testing. 111 inverse ARP. 17 models layered. 21 switching. 60 Mbps (megabits per second). configuring. 3-5 physical LANs. 35 read-only (ROM). 185 local intranets. 181 testing.39_1587131749_Index. 39. 82 link management identifiers (LMIs). 32 counts (DHCP). 157 networks. See LANs local collisions. 50.

108 NCP (Network Control Protocol). 40. 31 Organizational Unique Identifiers (OUIs). 108 internetworks. 36 options field (IP packets). 4 transport.qxd 7/28/06 9:00 AM Page 221 OSI (Open Source Initiative) Moran. 188 NEXT (near-end crosstalk). 207 multicasting (VTP). 129 IP address association. 49 Ethernet. 171 types. 4 session.39_1587131749_Index. 90 Class C Subnet. 155 Layer 4 connectivity. 192 dynamic. 4 model benefits. 164 no ip subnet-zero command. 17 functionality. 4 PDUs. 61. 4 presentation. 142 images. 55 Layer 3 schemes. 123 NICs (network interface cards). 4-5 LAN designs. See OSPF operating environments. 187 Layer 1 schemes. 157 paths (routers). 3 noise (LANs). 57 official certificates. 4 data link. 63 peer-to-peer. improving. 116 N names ACLs. 29 determining. 197 NVRAM (nonvolatile random-access memory). 29. 122-124 class boundaries. 107 NAT (network address translation). 61-62 overload. 55. 74. 99 convergence. 49-52 networks access layer. 155-156. 79 segments. 82 near-end crosstalk (NEXT). 187 collisions. 60 nodes of communication. 160 no cdp run command. 17 latency. 54 Layer 2 schemes. 30 troubleshooting. 27. See NAT Network Control Protocol (NCP). 51 performance. 122-123 number specifications (ACLs). 52 physical topology. 70 IP addresses. 82 network interface cards (NICs). 110. 160 no debug all command. 15 protocols. 157 . 122 subnetworks. 141 numbered ACLs. 49-52 no cdp enable command. 60 private. 4 OSI management model. 51-52 communication. ignoring. 15 OSI (Open Source Initiative) layers application. 30 cabling. See protocols 221 PSNs. Matthew. 207 Open Shortest Path First. 17 layer. 6 addresses. 9 devices (LANs). 35 O octets (IP addresses). 110 static. 11 designing. 63 network. 185 IOS naming conventions. 123 network address translation. 69. 3 Layer 3 connectivity. 70 signals. 39. 109 packets. 70 configuring. 4 physical.

96 troubleshooting. 182 switches. 105 encrypting. 65-66 hello packets. 35 . 77 power sum near-end crosstalk (PSNEXT). 168 ICMP messages. 95 interface costs. 50. 105 PAT (port address translation). compared. 28 testing. 33 security. 181 peer-to-peer networks. 8. 77 Point-to-Point Protocol. 123 power supplies (routers). 164-165 updates. 33 POTS (plain old telephone service). 79 packets ACL management. 82 PAR (positive acknowledgement and retransmission). 78 physical topology (networks). 167 troubleshooting. 33 number ranges. 54 OSI. 64. 94 priorities. 15 physical WAN connections. 110 paths. 93 databases.39_1587131749_Index. 91 permanent virtual circuits (PVCs). 109. 164 authentication. 22-23 OUIs (Organizational Unique Identifiers). 106 privileged EXEC mode. 83 overload (NAT). 95 loopback interface. 171 plain old telephone service (POTS). 44 physical layers LANs. 182 positive acknowledgement and retransmission (PAR). 33 passive-interface command. 77 ping command extended. 3-4 networks. 51 number assignments. 31 NAT. 31 PAP (Password Authentication Protocol). 35 PDUs (protocol data units). 44. 95 configuring. 22 default routes. See PPP port address translation (PAT). 23 IP. 24 hello. 155. 91 packets. 91 Password Authentication Protocol (PAP). 82 passwords console. 79 Personal Computer Memory Card International Association (PCMCIA). 15 out-of-band signaling. 23 hello/dead intervals. 28. 137 STP states. 44. 19-20 PCMCIA (Personal Computer Memory Card International Association). 19-20 padding field (IP packets). 12. compared. 181 TCP/IP. 4 WANs. 39 EIGRP. 93. 192 P packet-switched networks (PSNs).qxd 222 7/28/06 9:00 AM Page 222 OSI (Open Source Initiative) layers. 43 MAC address associations. propagating. 70 paths load balancing. 199 TCP/IP. 94 testing. 51 transport layer. 70 ports demarcation points. 155-157 overview. 155. 96 features. 106 virtual terminal. 32 Layer 3 connectivity. 51 per-packet load balancing. 4 OSPF (Open Shortest Path First). 35 phone calls (WANs).

82 session establishment. 181 protocol field (IP packets). 53 internetworks. 21 priorities OSPF. 83 interfaces. 30 RIP. 110 bindings. 20. 183 NCP. 163 ISDN. 74 protocol data units (PDUs). 6. 22 vector. 23 packets. 133 processes (DHCP). 147 protocols. 82 authentication. 82 NCP. 111 processes. 22 routing updates. 6. 21 system routes. 17 professional certifications. 53. 147 frame fields. compared. 111 processing frames. excluding. 58 LANs. 82 session establishment. 20. 145-146 enabling. 183 EIGRP. 64 configuring. 49 DHCP addresses. 92 exterior routes. 190 reference points. 24. viewing. 70 IP address allocation. 31 protocols application layer. 110. 82 PPP. 20. 111 distance vector. 71 message counts. 4 preventing loops. 9. 24 route summaries. 97 configuring. 208 protecting users (ACLs). 83. 190 RARP. 165 verifying.qxd 7/28/06 9:00 AM Page 223 protocols PPP (Point-to-Point Protocol). 30 privileged EXEC mode. 84 out-of-band signaling. 111 broadcasts. 111 configuring. 28. 97-98 topology tables. 145-146 enabling. 82 NCP. 64 configuring. 82 configured. 52 BOOTP. 82 authentication. 91 private addresses IP addresses. 94 routes. 25 223 features. 82. 82. 64. 22 interior routes. 96 DUAL algorithm. 21 load balancing. 30. 82 network. 145 encapsulation. 106. 20. 163-165 verifying.39_1587131749_Index. 71 CDP. 182 ARP. 164-165 verifying. 77 BRI. 83 PRI. 92 defined. 159-160 CHAP. 64 updates. 82 link-state. 111 starting/stopping. 15 PAP. 90 Linksys support. 146 PRI E1. 22 troubleshooting. 145-146 LCP. 177 LCP. 146 configuring. 145 encapsulation. 83-84. 30. 65 distance vector protocols. 98 ICMP. 190 presentation layer (OSI). 67 bandwidth. 186 networks. 24 troubleshooting. 164 . 66 multiprotocol support. 192 host IP addresses. 91 troubleshooting. 32 IGRP. 190 verifying. 145-146 LCP. 64 advanced features.

49 RIP (Routing Information Protocol). 133 radio frequency (RF). 15. 20. 4. 33 PDUs. 44. 35 Rapid Spanning Tree Protocol (RSTP). 208 Reverse Address Resolution Protocol (RARP). 116 WANs. 190-191 troubleshooting. 189. 58 restoring configuration files. 7 TCP communication. 90 Linksys support. 93 . 65. 54 reserved network IP addresses. 12 RARP (Reverse Address Resolution Protocol). 28 overview. 11 port states. 64 link-state. 201 RSTP. 205 LANs. 5-8. preventing. 22 listing of. 12. 123 PSNs (packet-switched networks). 22. 11 loop redundancy. 116 modes. 164 version 1.39_1587131749_Index. 79 PVCs (permanent virtual circuits). 164-165 verifying. 20. 93 routing. 20. 28 network communication. 190 remote collisions. 65 default administrative distances. 33 layers. 64. 30 RF (radio frequency). 129-130 routers. 83-84. 138 restricting vty access. 63 OSPF. 22. 193 multicasting. 117. 79 Q-R question marks (?). See RIP syntax. 32 UDP. 33 sliding windows. 182 network convergence. 182 reference points (ISDN). 20-22. 193 messages.qxd 224 7/28/06 9:00 AM Page 224 protocols version 1. 8 transport layer. 116 switch modes. 181 PAR. 22. 159 STP BIDs. 202 PSNEXT (power sum near-end crosstalk). 19. 188 OSI Layer 3. 65 version 2. 182 redundant connections. 21 load balancing. 22. 143 retaking the exam. 6. 30 read-only memory (ROM). 7 TCP segments. 50 rings. 65 version 2. 63 BGP. 6. 20 EIGRP. 65. 64 configuring. 91 troubleshooting. 127 IOS images. 171 switches. 24 requirements exam day. 161 TCP/IP DoS attacks. 33 hosts. 11 switching loops. 50 RAM (random-access memory). 39. 11 loops. 64-66 RIP. 49-50 reported distance field (EIGRP topology table). 185 repeaters (LANs). 22-23. See EIGRP IGRP. 99 OSI. 28 ports. router commands. 12 troubleshooting. 35 redundancy connections. 8 VTP. 113 configuring. 12 SNAP. 164 distance vector. compared.

19 default routes. 192 DHCP. 112 software compatibility. 195 Cisco. 105 testing. 52 segmenting. 90 propagating with OSPF. 99-100 NAT. filtering. 149 modes. 22 updates. 135 interfaces. 21 routing metrics. 171 route poisoning. 171 VTY lines. 17 paths. 188 OSI Layer 3. See EIGRP IGRP. 130 hostnames configuring. 37 CLI modes. 108 initial configuration example. 35-36 console TIA/EIA-232 port connections. 36 starting. 63 operating environments. 195 boot process. customizing. See RIP routed protocols. 90 EIGRP summaries. 91 loops avoiding. 50 rollover cables. 22 poisoning. 63 LED lights. 11 route source field (EIGRP topology table).qxd 7/28/06 9:00 AM Page 225 routing RJ-45 connectors. 91 routing DDR. 65 default administrative distances. 22 EXEC mode. 37 Linksys. 128 saving. 127-12. 64 link-state. 64-66 RIP. 126 vty. 145 routes default. 20-22 listing of. 52 troubleshooting. 89-91 deleting. 21 SNMP. 175 available commands. 90 successor. 36 networks class boundaries. 20 EIGRP. 21 protocols BGP. 36 commands. 22 feasible successor. 192 Frame Relay PVC. 92 verifying. 49. 20-22. viewing. 22 configuring. 63 OSPF.39_1587131749_Index. 90 functionality. 96 verifying. 164 distance vector. 133 flash. 24 interior. 99 internal components. 21 load balancing. 21 priorities. 54 communication. 91 static configuring. 133 backing up. enabling. 21 225 memory. 19-20 restoring. 184 preventing. 35 ROM Monitor (ROMMON). improving. 22-23. 195 traffic. 35 LANs. 19 . 192 registers. compared. 36 packets. 20. 178 metrics. 123 ROM (read-only memory). 36 ROMMON (ROM Monitor). 192 connecting. 64. 24 routers ACL placement. 196 configuration commands. 195 console. 24 route status field (EIGRP topology table). 24 system. 37 convergence. 36 root bridges. 97-98 exterior. 74 as WAN devices.

126 scalability (LANs). 137 user protection. 111 show ip dhcp server statistics command. 89. See RIP RSTP (Rapid Spanning Tree Protocol). 54 ScTP (screened twisted pair). 69 storing configuration files. 31 Spanning Tree Protocol. 190 starting. 111 storage-area networks (SANs). 8 sending BPDUs. 172 show isdn status command. 163 show ip route command. 163. 177 show ip dhcp binding command. 69 saving router configurations. 4 sessions PPP. 12 runts. 137 static NAT. 70 stopping DHCP. 36 SONET (Synchronous Optical Network). 111 show ip interface command. 19. 159 show cdp neighbors detail command. 98. 111 routers. 122 show access-lists command. 45. 122 SIMMs (single inline memory modules). 172 show ip rip database command. 115. 159 show cdp neighbors command. 175 show cdp command. 39. 100-102. 11 serial communication (WANs). 7 SMTP (Simple Mail Transfer Protocol). 6 SNAP (Subnetwork Access Protocol). 172 show flash command. 112 software compatibility (routers). 160 show commands. 186 S SANs (storage-area networks). 165 Routing Information Protocol. 175 show ip protocols command. 35 sliding windows (TCP/IP). 92 verifying. 77 source address field (IP packets). 177 show running config command. 115 signals (network). configuring. 81 segments LANs. 201 tables. 190-191 troubleshooting.qxd 226 7/28/06 9:00 AM Page 226 routing syntax. 175 EIGRP. 126 . 6. 84 session layer (OSI). 40. 108 static routes administrative distance. 159 SNMP (Simple Network Management Protocol). 163 troubleshooting. 195 static MAC address configuration. 175 show version command. 70 TCP. 36 show vlan command. 74 stars. 122 security ports. 74 WANs. 165 RIP. 16. 7 shielded twisted pair (STP). 106-107 ACLs. 165 IGRP. 191 service profile identifiers (SPIDs). 81 serial interfaces. 35 single inline memory modules (SIMMs). troubleshooting. 19 configuring. 91 deleting. 134 show interface command.39_1587131749_Index. 49 starting CDP. 15. See STP SPIDs (service profile identifiers). 63 networks. 164-165 show controllers command. 159 DHCP. 90 static VLANs. 163-165 OSPF. 130 show history command. 84 standard ACLs.

150 VLANs. 12. 60 network addresses. 182 BIDs. 60 two borrowed bits. 99 OSI. 33 sliding windows. 44-46 frames forwarding. 53 ports. 61 Subnetwork Access Protocol (SNAP). identifying. 17 backing up. 6-8 network communication. 182 trunks. compared. 9 internet. 117 successor routes. 85 virtual circuits. determining. 79 WANs. 12 troubleshooting. 6 transport. 115 switching loops. 125-126 dividing into VLANs. 11. 30 subset advertisements. 17 port security. 11 processing. 51 host traffic. 136 Catalyst 2950. 137-138 BIDs. 122 straight-through cables. 24 summary advertisements. 58 eight borrowed bits. 5-6. 28 application. 79 switched circuits (WANs). 33 layers. 121 TCP segments. 11 BPDUs. sending. 22 T tables routing. 187 IP addresses. 11. 33 PDUs. 44. 182 network convergence. 59 VLSMs. 135 customizing. 17 LANs. 136-137 microsegmentation. 163 topology. 123 subinterfaces configuring. 182 redundant connections. 138 static VLANs. 28 overview. 196 communication. 51 configuring Catalyst 1900.qxd 7/28/06 9:00 AM Page 227 TCP/IP (Transmission Control Protocol/Internet Protocol) STP (Spanning Tree Protocol). 17 network functionality. 117 SVCs (switched virtual circuits). 33 hosts. regulating. 7 . compared. 117 subnet masks VLSMs. 11 switching loops. 60 seven borrowed bits. 12 Synchronous Optical Network (SONET). 28 ports. 11 port states. 159 subnetworks. 161 STP (shielded twisted pair). 79 switches adaptive cut-through mode. 181 PAR. 8 TCP/IP (Transmission Control Protocol/Internet Protocol) DoS attacks. 113 STP. 49 connections. 6 network access. 4. 19. 53 local machines. 51 MAC addresses. 58 borrowed bits with corresponding mask. 136 clearing. improving. 70 227 Frame Relay. 60 wildcard masks. 11 commands. preventing. 40 subnetting Class C networks. 24 Tbps (terabits per second). 77 system routes (IGRP). 137 restoring. 16 content addressable memory. 11 loop redundancy.39_1587131749_Index.

4 ports. 172 DDR. 171 OSI model. 167 terabits per second (Tbps). 165 protocols. 171 routing. 32 TDM (time division multiplexing). 157 OSI model. 168 IGRP. 167 OSPF. 108 tftpdnld command. 201 tables. 31 Token Ring Layer 2 technology. 115 turning off CDP. See also testing commands. 115 VLANs. 7 segments. 81 time to live field (IP packets). 171-172 traffic controlling. 7 TCP communication. 193 connections. 194 updates link-state protocols. 178 DoS attacks. 160 EIGRP route summaries. 164-165 RIP. 121 terminal editing command. 15 physical. 155 Layer 4 connectivity. 167-168 LANs CDP. 199 OSPF. 161.qxd 228 7/28/06 9:00 AM Page 228 TCP/IP (Transmission Control Protocol/Internet Protocol) TCP communication. 159-161 commands. 165 extended ping command. 182 TCP/IP. 199-201 WANs Frame Relay. 161 VLANs. 22 OSPF. 9 time division multiplexing (TDM). 97 type of service field (IP packets). 15 tables. 161 switches. 172 terminal no editing command. 163 STP. 91 . 134 testing. 106 unshielded twisted pair (UTP). 122-123. 8 undebug all command. 171 networks. 134 terminal history size command. 32 flow control. 5 topologies LANs. 96 routers. 31 traceroute command. 8 transport layer. 6-7 ports. 81 telnet command. 7 troubleshooting. 177 protocols. 53 Transmission Control Protocol/Internet Protocol. 130 three-layer designs (WANs). 177 trunk configuring. 22-23 routes.39_1587131749_Index. See TCP/IP transport layer OSI. 164 unencrypted passwords. 33 EIGRP. 73 filtering. 134 terminal monitor command. 199-201 Layer 3 connectivity. 31 U-V UDP (User Datagram Protocol). 178 ISDNs. 6. 202 serial connections. See also troubleshooting Layer 3 connectivity. 165 routers. 183 logical. 161 trunk connections. 52 hosts. 24 total length field (IP packets). 163-164. 81 three-layer hierarchical model. 155-156. 165 IP addresses. 8 sessions.

110 OSPF priorities. 85 LANs. 130 MAC addresses. 98 Frame Relay. 145 connections. 113 configuring. 114 static commands. 143 configuring. 45 equipment. 117. 43 speeds. 79 Frame Relay networks. 110 virtual circuits. 199-201 trunking. 159 Cisco neighboring devices. 136 memory. 70 overview. 177 NAT configurations. 51 verifying ACLs. 43 provider central office. 43 branch networks. 116 modes. 77 virtual terminal passwords. 54 viewing cdp-enabled devices. 163-164 VLAN configuration. 8 users. configuring. 114-115 version field (IP packets). 114-115 VLAN Trunking Protocol. 122-123. 147. 116 deleting. 70 troubleshooting. 193 subinterfaces. 74. 113 global configuration mode. 113 configuring. 149 EIGRP. 44. 82 communication service providers. 178 ISDNs. 193 multicasting. 193 multicasting. 79 types. 193 messages. 194 variable-length subnet masks. controlling. 94 routes. 69 Cisco HDLC encapsulation. 92 interfaces. 105 vlan database command. 117 verifying. 69. 70 features. 192 lines. 159 commands. 36 NAT packets. 116 switch modes. 69. 77 VTP (VLAN Trunking Protocol).qxd 7/28/06 9:00 AM Page 229 WANs (wide-area networks) User Datagram Protocol (UDP). 175 DDR configuration. 43 digital. See VLSMs VCCs (vertical cross-connects). 93 IP address subnets. 43 demarcation points. 197-199 PPP encapsulation. 114 229 customizing. 113 membership. 43. 161. 115 dividing switches into. protecting. 92 DHCP. 74 UTP (unshielded twisted pair). 117 messages. 111 flash. 116 vty access. 31 vertical cross-connects (VCCs). 116 modes. See VCs Virtual LANs. 114-115 vlan database command. 115 VTP configuring. 116 VLSMs (variable-length subnet masks). 193 static. 150. 116 switch modes. 90 routing protocols. 81 cabling. 54 VCs (virtual circuits).39_1587131749_Index. See VTP VLANs (Virtual LANs). 74 W WANs (wide-area networks). See VLANs virtual private networks (VPNs). 133 configured protocols. restricting. 43 HSSI. 77 . 78 configuring commands. 60. 43 switched circuits. 61 VPNs (virtual private networks).

85 frames. 44-46. configuring. 77 physical layers. 44 gateways to LANs. 149-150 connections. 207 Wikipedia. 85 inverse ARP messages. 82. 50 X-Y-Z X. 145 security. 83 PRI. 146 configuring. 147 packet-switched networks.qxd 230 7/28/06 9:00 AM Page 230 WANs (wide-area networks) data communication. 44. 79-80 three-layer designs. 3 wildcard masks ACLs. See WANs Wikipedia website. 146 PRI E1. 81 services. configuring. 81 internetworks. 83-84 verifying. 190 protocols. 69 designing. 86 LAN connections. 40 WLANs (wireless LANs). 130 YAOMC (Yet Another OSI Model Chart). 83 reference points. 85 virtual circuits. 145-146 LCP. 83 interfaces. 85 configuring. 147 protocols. 85 LMIs. 177-178 websites certificate online support. 44. 3-4 . 202 routers connecting. 44 physical connections. 78 PPP authentication. 78 DDR. 85 switches. 84 out-of-band signaling. 145 encapsulation. 3 wide-area networks. 82 NCP. 189. compared. 45. 186 flat topology. 78 high-bandwidth/low latency. 81 encapsulation. configuring. 45. 36 as WAN devices. 81 Frame Relay. 44 data link layers. 82 session establishment.39_1587131749_Index. 80 xmodem command. 73 subnet masks. 81 troubleshooting. 44 phone calls. 145-146 enabling. 147-149 defined. 71-72. 80 ISDN BRI. 81 serial communication.25 WAN service. 147 frame fields.

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