0945_01f.book Page i Wednesday, July 2, 2003 3:53 PM CCNA Self-Study CCNA INTRO Exam Certification Guide Wendell Odom, CCIE No. 1624 Cisco Press Cisco Press 201 West 103rd Street Indianapolis, IN 46290 USA 0945_01f.book Page ii Wednesday, July 2, 2003 3:53 PM ii CCNA INTRO Exam Certification Guide Wendell Odom Copyright© 2004 Cisco Systems, Inc. Published by: Cisco Press 201 West 103rd Street Indianapolis, IN 46290 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 permis- sion 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 2003 Library of Congress Cataloging-in-Publication Number: 2003104998 ISBN: 1-58720-094-5 Warning and Disclaimer This book is designed to provide information about selected topics for the Introduction to Cisco Networking Technologies (INTRO) exam for the CCNA certification. 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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Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. 0945_01f.book Page iii Wednesday, July 2, 2003 3:53 PM iii Publisher: John Wait Cisco Representative: Anthony Wolfenden Editor-In-Chief: John Kane Cisco Press Program Manager:Sonia Torres Chavez Executive Editor: Brett Bartow Cisco Marketing Communications Manager:Scott Miller Managing Editor: Patrick Kanouse Cisco Marketing Program Manager:Edie Quiroz Development Editor: Christopher Cleveland Technical Editors:Elan Beer, Lynn Maynes, Martin Walshaw Project Editor: Marc Fowler Copy Editor: Krista Hansing Team Coordinator: Tammi Barnett Book Designer: Louisa Adair Cover Designer: Louisa Adair Compositor: Mark Shirar Indexer: Tim Wright 0945_01f.book Page iv Wednesday, July 2, 2003 3:53 PM iv About the Author Wendell Odom, CCIE No. 1624, is a senior instructor with Skyline Computer (www.skylinecomputer.com), where he currently teaches courses on QoS, CCNA, and CCIE lab preparation. Wendell has worked in the networking arena for 20 years, with jobs in pre- and post-sales technical consulting, teaching, and course development. He has authored portions of more than 12 courses, including topics such as IP routing, MPLS, Cisco WAN switches, SNA protocols, and LAN troubleshooting. He is author of three previous editions of the CCNA Exam Certification Guide as well as the Cisco Press DQOS Exam Certification Guide. About the Technical Reviewers Elan Beer, CCIE No. 1837, CCSI No. 94008, is a Senior Consultant and Certified Cisco Instructor. Elan’s internetworking expertise is recognized internationally through his global consulting and training engagements. As one of the industry’s top internetworking consultants and Cisco instructors, Elan has utilized his expertise to design, implement, and deploy multiprotocol networks for a wide range of international clientele. As a senior instructor and course developer, Elan has designed and presented public and implementation-specific technical courses spanning many of today’s top technologies. Elan can be reached via e-mail at [email protected]. Lynn Maynes, CCIE No. 6569, is a senior network engineer with Sprint Managed Network Services specializing in network design, architecture and security for large-scale networks worldwide. He has more than 9 years of experience in computer networking and is a co- author of the Cisco Press book CCNA Practical Studies. He holds a bachelor’s degree in international business from Westminster College. Martin Walshaw, CCIE No. 5629, CISSP, CCNP, CCDP, is a systems engineer working for Cisco Systems in the Enterprise Line of Business in South Africa. His areas of specialty include convergence, security, and content delivery networking, which keeps him busy both night and day. During the last 15 years or so, Martin has dabbled in many aspects of the IT industry, ranging from programming in RPG III and COBOL to PC sales. When Martin is not working, he likes to spend all of his available time with his patient wife, Val, and his sons, Joshua and Callum. Without their patience, understanding, and support, projects such as this would not be possible. 0945_01f.book Page v Wednesday, July 2, 2003 3:53 PM v Dedications Chris Cleveland is the best Development Editor I could imagine working with. So, instead of just the usual “Thanks Chris for doing an excellent job,” I’d like to dedicate this book to Chris. Chris, it’s an absolute pleasure to work with the best in the business —thanks for your fantastic help and support! Acknowledgments The technical editing team for this book and its companion volume was fantastic! Not only did they find where I had simply written the wrong technical facts, but they also helped me find new, more interesting, and clearer ways to convey certain facts about networking. Lynn was particular helpful with comments that helped keep small sections in line with the overall theme of the chapter—a skill I’m sure he developed as a result of having written books himself. Martin helped a lot with technical detail and perspectives from what customers see every day today. And Elan excelled in noticing both the small nit-picky errors and the significant technical problems. (And that’s not an insult—every technical author loves help in finding the small problems!) Together, these three gentlemen formed a great team, with complementary skills. Thanks so much, guys! The production team, headed by Patrick Kanouse, did its usual excellent job. Like the behind-the-scenes people in many businesses, their specific efforts may not be obvious to the public, but it’s no less appreciated by me. In particular, Marc Fowler, the project editor, did an incredible job working through these two books on a very tight schedule, with his usual excellent work. You folks make me look good on paper all the time—if only you could be in charge of my wardrobe, too—I’d look good all the time! Brett Bartow, executive editor, did his usual New-York-Yankees-like job in helping steer these two projects to completion. In between talking about sports, Brett worked through the many changes in direction with this book and helped guide us to the right product. And, yes, so the whole world knows, he did pick an Atlanta Braves player, John Smoltz, for his fantasy league baseball team—again proving he’s a really smart guy. Chris “develops” books for Cisco Press. What does that mean? Well, it means that he takes the Word documents and figures from geeky authors, and makes their writing become understandable. He takes the input from technical editors, and combines all the comments into a single word document, making the author’s life easier. He constantly finds ways to rephrase, reword, and improve the manuscript. He manages all the work with the authors. And he always works to optimize the author’s time, taking away some of the unpleasant part of the work, so that the author can worry about the technical details. Chris has worked with me on 6 projects now, and every time, he has done an excellent job. His work ethic goes far beyond the call of duty, and his performance is consistently excellent. To quote a few other authors as well: “Chris has taken all of the difficulty (of writing) out of the picture”, “Chris has absolutely spoiled me and completely amazes me”, and “He even helped me with my daughter’s homework”. Whatever, however, to make the book better, with an eye towards the least pain for the author, Chris is on top of it. Thanks, Chris, for all you do! 0945_01f.book Page vi Wednesday, July 2, 2003 3:53 PM vi Contents at a Glance Introduction xvii PART I: Networking Fundamentals 3 Chapter 1 Introduction to Computer Networking Concepts 5 Chapter 2 The TCP/IP and OSI Networking Models 15 Chapter 3 Data Link Layer Fundamentals: Ethernet LANs 43 Chapter 4 Fundamentals of WANs 77 Chapter 5 Fundamentals of IP 109 Chapter 6 Fundamentals of TCP and UDP 145 PART II: Operating Cisco Devices 169 Chapter 7 Operating Cisco Routers 171 Chapter 8 Operating Cisco LAN Switches 209 PART III: LAN Switching 227 Chapter 9 Cisco LAN Switching Basics 229 Chapter 10 Virtual LANs and Trunking 259 Chapter 11 LAN Cabling, Standards, and Topologies 279 PART IV: TCP/IP 311 Chapter 12 IP Addressing and Subnetting 313 Chapter 13 Basic Router Configuration and Operation 363 Chapter 14 Introduction to Dynamic Routing Protocols 403 PART V: Wide-Area Networking 427 Chapter 15 Remote Access Technologies 429 PART VI: Final Preparation 477 Chapter 16 Final Preparation 479 PART VII: Appendixes 497 Appendix A Answers to the “Do I Know This Already?” Quizzes and Q&A Sections 499 Appendix B Binary/Decimal Conversion Chart 565 Appendix C Using the Simulation Software for Hands-on Exercises 571 Glossary 577 Index 593 0945_01f.book Page vii Wednesday, July 2, 2003 3:53 PM vii Contents Introduction xvii Part I Networking Fundamentals 3 Chapter 1 Introduction to Computer Networking Concepts 5 Perspectives on Networking 5 The Flintstones Network: The First Computer Network? 7 Chapter 2 The TCP/IP and OSI Networking Models 15 “Do I Know This Already?” Quiz 16 Foundation Topics 20 The TCP/IP Protocol Architecture 21 The TCP/IP Application Layer 22 The TCP/IP Transport Layer 24 The TCP/IP Internetwork Layer 26 The TCP/IP Network Interface Layer 27 Data Encapsulation 29 OSI Reference Model 31 OSI Layers 31 OSI Layering Concepts and Benefits 34 OSI Terminology 35 OSI Summary 37 Foundation Summary 38 Q&A 41 Chapter 3 Data Link Layer Fundamentals: Ethernet LANs 43 “Do I Know This Already?” Quiz 43 Foundation Topics 47 OSI Perspectives on Local-Area Networks 47 Typical LAN Features for OSI Layer 1 47 Typical LAN Features for OSI Layer 2 50 Data Link Function 1: Arbitration 50 Data Link Function 2: Addressing 51 Data Link Function 3: Error Detection 51 Data Link Function 4: Identifying the Encapsulated Data 52 Early Ethernet Standards 52 Standards Overview 53 The Original Ethernet Standards: 10BASE2 and 10BASE5 53 Repeaters 55 10BASE-T Ethernet 56 Ethernet 10BASE-T Cabling 57 10BASE-T Hubs 59 Performance Issues: Collisions and Duplex Settings 60 Reducing Collisions Through LAN Switching 60 Eliminating Collisions to Allow Full-Duplex Ethernet 62 0945_01f.book Page viii Wednesday, July 2, 2003 3:53 PM viii Ethernet Data-Link Protocols 63 Ethernet Addressing 64 Ethernet Framing 65 Identifying the Data Inside an Ethernet Frame 66 Layer 2 Ethernet Summary 68 Recent Ethernet Standards 68 Fast Ethernet 68 Gigabit Ethernet 69 Foundation Summary 70 Q&A 74 Chapter 4 Fundamentals of WANs 77 “Do I Know This Already?” Quiz 77 Foundation Topics 81 OSI Layer 1 for Point-to-Point WANs 81 WAN Connections from the Customer Viewpoint 84 WAN Cabling Standards 85 Clock Rates, DCE, and DTE 88 Link Speeds Offered by Telcos 89 OSI Layer 2 for Point-to-Point WANs 91 HDLC 91 Point-to-Point Protocol 92 Other Point-to-Point WAN Data-Link Protocols 94 Synchronization 94 Point-to-Point WAN Summary 95 Packet-Switching Services 95 Frame Relay 96 Frame Relay Basics 97 ATM and SONET 100 SONET 100 ATM 101 WAN Terminology Related to Packet Switching 102 Foundation Summary 104 Q&A 106 Chapter 5 Fundamentals of IP 109 “Do I Know This Already?” Quiz 109 Foundation Topics 114 Typical Features of OSI Layer 3 114 Routing (Path Selection) 114 PC1’s Logic: Sending Data to a Nearby Router 114 R1 and R2’s Logic: Routing Data Across the Network 115 R3’s Logic: Delivering Data to the End Destination 116 Network Layer Interaction with the Data Link Layer 116 0945_01f.book Page ix Wednesday, July 2, 2003 3:53 PM ix Network Layer (Layer 3) Addressing 118 Example Layer 3 Address Structures 119 Routing Protocols 119 IP Addressing Fundamentals 120 IP Addressing Definitions 120 How IP Addresses Are Grouped Together 121 Classes of Networks 122 The Actual Class A, B, and C Network Numbers 124 IP Subnetting 124 Network Layer Utilities 127 Address Resolution Protocol and the Domain Name System 127 ICMP Echo and the ping Command 130 RARP, BOOTP, and DHCP 130 IP Routing and Routing Protocols 133 IP Routing Protocols 135 Foundation Summary 138 Q&A 142 Chapter 6 Fundamentals of TCP and UDP 145 “Do I Know This Already?” Quiz 145 Foundation Topics 149 Typical Features of OSI Layer 4 149 The Transmission Control Protocol 150 Multiplexing Using TCP Port Numbers 151 Popular TCP/IP Applications 154 Error Recovery (Reliability) 155 Flow Control Using Windowing 156 Connection Establishment and Termination 158 Connectionless and Connection-Oriented Protocols 159 Data Segmentation and Ordered Data Transfer 160 TCP Function Summary 161 The User Datagram Protocol 161 Foundation Summary 164 Q&A 167 Part II Operating Cisco Devices 169 Chapter 7 Operating Cisco Routers 171 “Do I Know This Already?” Quiz 171 Foundation Topics 176 The Cisco IOS Software Command-Line Interface 176 Access to the CLI 176 CLI Help Features 179 The debug and show Commands 181 0945_01f.book Page x Wednesday, July 2, 2003 3:53 PM x Configuring Cisco IOS Software 181 Example Configuration Process 183 Router Memory, Processors, and Interfaces 187 Managing Configuration Files 188 Viewing the Configuration and Old-Style Configuration Commands 190 Initial Configuration (Setup Mode) 190 Upgrading Cisco IOS Software and the Cisco IOS Software Boot Process 194 Upgrading a Cisco IOS Software Image into Flash Memory 194 The Cisco IOS Software Boot Sequence 197 Foundation Summary 200 Q&A 204 Chapter 8 Operating Cisco LAN Switches 209 “Do I Know This Already?” Quiz 209 Foundation Topics 213 Navigating Through a Cisco 2950 Switch 213 2950 Series Features and Functions 213 2950 Switch Operating System 214 Accessing the Cisco 2950 Switch CLI 215 Switch Initialization 216 Switch LEDs During POST 216 Initial Configuration Mode 218 Configuring 2950 IOS Software 220 Foundation Summary 221 Q&A 223 Part III LAN Switching 227 Chapter 9 Cisco LAN Switching Basics 229 “Do I Know This Already?” Quiz 229 Foundation Topics 234 The Case for Bridging and Switching 234 Transparent Bridging 236 The Forward Versus Filter Decision 237 How Bridges Learn MAC Addresses 239 Forwarding Unknown Unicasts and Broadcasts 240 LAN Switching 240 Full-Duplex Ethernet 242 Internal Processing on Cisco Switches 242 Speed and Autonegotiation 244 Summary: Bridges and Switches 244 LAN Segmentation 245 The Need for Spanning Tree 248 How Spanning Tree Works 249 Foundation Summary 252 Q&A 255