xxi Troubleshooting Router Connections Using the show controllers serial Command . . . . . . . . . . . . . . . . . . . . . . . . . .805 Introduction to debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .806 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .809 Key Terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .810 Check Your Understanding . . . . . . . . . . . . . . . . . . . . . . . . . . . .810 Chapter 19 Intermediate TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .815 The TCP/IP Protocol Suite . . . . . . . . . . . . . . . . . . . . . . . . . . . .815 TCP/IP Protocol Stack and the Application Layer . . . . . . . . .816 TCP/IP Protocol Stack and the Transport Layer. . . . . . . . . . . 818 TCP and UDP Segment Format . . . . . . . . . . . . . . . . . . . . . . .819 TCP Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .820 Three-Way Handshake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .821 Denial-of-Service Attacks During Synchronization. . . . . . . . .822 Windowing and Window Size . . . . . . . . . . . . . . . . . . . . . . . . 823 Sequencing Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .825 Positive ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .826 UDP Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .827 Overview of Transport Layer Ports . . . . . . . . . . . . . . . . . . . . . .828 Multiple Conversations Between Hosts . . . . . . . . . . . . . . . . .828 Ports for Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .831 Ports for Clients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .832 Port Numbering and Well-Known Ports . . . . . . . . . . . . . . . .832 Example of Multiple Sessions Between Hosts . . . . . . . . . . . .832 Comparison of MAC Addresses, IP Addresses, and Port Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .833 TCP/IP and the Internet Layer. . . . . . . . . . . . . . . . . . . . . . . . . . 833 How ARP Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .834 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .835 Key Terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .836 Check Your Understanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836 Chapter 20 Access Control Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .841 ACL Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841 Why Create ACLs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .843 Creating an ACL: Why Order Matters . . . . . . . . . . . . . . . . . . .844 Using ACLs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .844 1102.book Page xxi Tuesday, May 20, 2003 2:53 PM xxii How ACLs Work. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .845 ACL Configuration Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . .847 Assigning a Unique Number to Each ACL. . . . . . . . . . . . . . . . .847 Using Wildcard Mask Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . .848 Using the Wildcard any . . . . . . . . . . . . . . . . . . . . . . . . . . . . .850 Using the Wildcard host . . . . . . . . . . . . . . . . . . . . . . . . . . . . .851 Standard ACLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .852 Extended ACLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .855 Configuring Extended ACLs for ICMP. . . . . . . . . . . . . . . . . .861 Configuring Extended ACLs for IGMP . . . . . . . . . . . . . . . . .861 Configuring Extended ACLs for TCP . . . . . . . . . . . . . . . . . . .861 Configuring Extended ACLs for UDP. . . . . . . . . . . . . . . . . . .862 Extended ACL Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . .862 Named ACLs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .863 Placing ACLs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .866 Firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .867 Using ACLs with Firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . .868 Restricting Virtual Terminal Access . . . . . . . . . . . . . . . . . . . . . .869 Verifying ACLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .870 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .871 Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .872 Check Your Understanding . . . . . . . . . . . . . . . . . . . . . . . . . . . .872 Part III Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .877 Appendix A Structured Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .879 Mounting Jacks in Drywall . . . . . . . . . . . . . . . . . . . . . . . . . .928 Mounting Jacks in Plaster . . . . . . . . . . . . . . . . . . . . . . . . . . .929 Mounting Jacks in Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . .930 Flush-Mounting a Jack in a Wall . . . . . . . . . . . . . . . . . . . . . .930 Pulling Cable to the Jacks. . . . . . . . . . . . . . . . . . . . . . . . . . . .930 Fishing Cable from Below a Wall . . . . . . . . . . . . . . . . . . . . . .931 Appendix B Glossary of Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .979 Appendix C Check Your Understanding Answer Key. . . . . . . . . . . . . . . . . .1009 Index 1047 1102.book Page xxii Tuesday, May 20, 2003 2:53 PM xxiii Cisco Systems Networking Icon Legend Cisco Systems, Inc., uses a standardized set of icons to represent devices in network topology illustrations. The following icon legend shows the most commonly used icons that you might encounter throughout this book. DSU/CSU Router Bridge Hub DSU/CSU Catalyst Switch Multilayer Switch ATM Switch ISDN/Frame Relay Switch Communication Server Gateway Access Server PC with Software PC Sun Workstation Macintosh Terminal File Server Web Server Cisco Works Workstation Printer Laptop Front End Processor Cluster Controller Modem Network Cloud Token Ring Token Ring Line: Ethernet FDDI FDDI Line: Serial Line: Switched Serial IBM Mainframe 1102.book Page xxiii Tuesday, May 20, 2003 2:53 PM xxiv Command Syntax Conventions The conventions used to present command syntax in this book are the same conven- tions used in the Cisco IOS Software Command Reference. The Command Reference describes these conventions as follows: ■ Vertical bars (|) separate alternative, mutually exclusive elements. ■ Square brackets ([ ]) indicate optional elements. ■ Braces ({ }) indicate a required choice. ■ Braces within brackets ([{ }]) indicate a required choice within an optional element. ■ Boldface indicates commands and keywords that are entered exactly as shown. ■ Italic indicates arguments for which you supply values. 1102.book Page xxiv Tuesday, May 20, 2003 2:53 PM xxv Foreword Throughout the world, the Internet has brought tremendous new opportunities for individuals and their employers. Companies and other organizations are seeing dramatic increases in productivity by investing in robust networking capabilities. Some studies have shown measurable productivity improvements in entire economies. The promise of enhanced efficiency, profitability, and standard of living is real and growing. Such productivity gains aren’t achieved by simply purchasing networking equipment. Skilled professionals are needed to plan, design, install, deploy, configure, operate, maintain, and troubleshoot today’s networks. Network managers must assure that they have planned for network security and for continued operation. They need to design for the required performance level in their organization. They must implement new capabilities as the demands of their organization, and its reliance on the network, expands. To meet the many educational needs of the internetworking community, Cisco Systems established the Cisco Networking Academy Program. The Networking Academy is a comprehensive learning program that provides students with the Internet technology skills essential in a global economy. The Networking Academy integrates face-to-face teaching, web-based content, online assessment, student performance tracking, hands-on labs, instructor training and support, and preparation for industry-standard certifications. The Networking Academy continually raises the bar on blended learning and educational processes. The Internet-based assessment and instructor support systems are some of the most extensive and validated ever developed, including a 24/7 customer service system for Networking Academy instructors. Through community feedback and elec- tronic assessment, the Networking Academy adapts the curriculum to improve outcomes and student achievement. The Cisco Global Learning Network infrastructure designed for the Networking Academy delivers a rich, interactive, and personalized curriculum to students worldwide. The Internet has the power to change the way people work, live, play, and learn, and the Cisco Networking Academy Program is in the forefront of this transformation. This Cisco Press title is one of a series of best-selling companion titles for the Cisco Networking Academy Program. Designed by Cisco Worldwide Education and Cisco Press, these books provide integrated support for the online learning content that is made available to Academies all over the world. These Cisco Press books are the only authorized books for the Networking Academy by Cisco Systems, and provide print and CD-ROM materials that ensure the greatest possible learning experience for Networking Academy students. 1102.book Page xxv Tuesday, May 20, 2003 2:53 PM xxvi I hope you are successful as you embark on your learning path with Cisco Systems and the Internet. I also hope that you will choose to continue your learning after you com- plete the Networking Academy curriculum. In addition to its Cisco Networking Academy Program titles, Cisco Press also publishes an extensive list of networking technology and certification publications that provide a wide range of resources. Cisco Systems has also established a network of professional training companies—the Cisco Learning Partners—who provide a full range of Cisco training courses. They offer training in many formats, including e-learning, self-paced, and instructor-led classes. Their instructors are Cisco certified, and Cisco creates their materials. When you are ready, please visit the Learning & Events area on Cisco.com to learn about all the educational support that Cisco and its partners have to offer. Thank you for choosing this book and the Cisco Networking Academy Program. Kevin Warner Senior Director, Marketing Worldwide Education Cisco Systems, Inc. 1102.book Page xxvi Tuesday, May 20, 2003 2:53 PM xxvii Introduction Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Third Edition, supplements your classroom and laboratory experience with the Cisco Networking Academy Program, whose curriculum is designed to empower you to enter employment or further education and training in the computer networking field. This book trains you beyond the online materials that you already have used in this program, and introduces you to topics pertaining to the Cisco Certified Network Associate (CCNA) certification exam. This book closely follows the style and format that Cisco Systems has incorporated into the curriculum. This book introduces and extends your knowledge and practical experience with the design, configuration, and maintenance of local-area networks (LANs). The concepts covered in this book enable you to develop practical experience in skills related to cabling, routing, IP addressing, routing protocols, and network troubleshooting. This book introduces the OSI model, discusses collisions and segmentations, and includes a new chapter on Ethernet technologies and Ethernet switching. This Companion Guide also features greatly enhanced chapters on IOS and TCP/IP and an additional chapter on access control lists. This book not only prepares you for the CCNA certification exam, but also for the CompTIA Network+ certification exam. The Goal of This Book The goal of this book is to educate you about Cisco supported networking technologies, and to help you understand how to design and build networks and to configure Cisco routers. It is designed for use in conjunction with the Cisco Networking Academy Program online curriculum. The Audience for This Book This book’s main audience is students interested in networking technologies. In partic- ular, it is targeted toward students in the Cisco Networking Academy Program. In the classroom, this book can serve as a supplement to the online curriculum. This book is also appropriate for corporate training faculty and staff members, as well as general users. The book’s user-friendly, nontechnical approach is ideal for readers who prefer to stay away from technical manuals. 1102.book Page xxvii Tuesday, May 20, 2003 2:53 PM xxviii Book Features Many of this book’s features help facilitate a full understanding of the networking and routing covered in this book: ■ Objectives—Each chapter starts with a list of objectives that should be mastered by the end of the chapter. The objectives provide a reference of the concepts covered in the chapter. ■ Figures, examples, tables, and scenarios—This book contains figures, examples, and tables that help explain theories, concepts, commands, and setup sequences that reinforce concepts and help visualize the content covered in the chapter. In addition, the specific scenarios provide real-life situations that detail the problem and the solution. ■ Chapter summaries—At the end of each chapter is a summary of the concepts covered in the chapter. It provides a synopsis of the chapter and serves as a study aid. ■ Key terms—Each chapter includes a list of defined key terms that are covered in the chapter. These terms serve as a study aid. In addition, the key terms reinforce the concepts introduced in the chapter and help you understand the chapter material before you move on to new concepts. You can find the key terms high- lighted in blue throughout the chapter where they are used in practice. ■ Check Your Understanding questions—Review questions, presented at the end of each chapter, serve as an assessment. In addition, the questions reinforce the con- cepts introduced in the chapter and help test your understanding before you move on to new chapters. ■ Lab Activity references—Throughout the book are references to worksheet and lab activities found in Cisco Networking Academy Program CCNA 1 and 2 Lab Companion, Third Edition. These labs help you make a connection between theory and practice. How This Book Is Organized This book is divided into 20 chapters and 3 appendixes: ■ Chapter 1, “Introduction to Networking,” presents the basics of connecting to the Internet. It also introduces different number systems and the processes used to convert a number from one number system to another. This chapter corre- sponds to the Module 1 content from the CCNA 1 online curriculum. 1102.book Page xxviii Tuesday, May 20, 2003 2:53 PM xxix ■ Chapter 2, “Networking Fundamentals,” introduces some of the terminology used by networking professionals and various types of computer networks. It also describes how the OSI reference model networking scheme supports net- working standards. In addition, this chapter describes the basic functions that occur at each layer of the OSI model. Finally, this chapter describes various network devices and networking topologies. This chapter corresponds to the Module 2 content from the CCNA 1 online curriculum. ■ Chapter 3, “Networking Media,” introduces the basic theory of electricity, which provides a foundation for understanding networking at the physical layer of the OSI model. This chapter also discusses different types of networking media that are used at the physical layer, including shielded twisted-pair cable, unshielded twisted-pair cable, coaxial cable, and fiber-optic cable, as well as wireless media. This chapter corresponds to the Module 3 content from the CCNA 1 online curriculum. ■ Chapter 4, “Cable Testing and Cabling LANs and WANs,” describes issues related to the testing of media used for physical layer connectivity in local-area networks (LANs). Networking media is literally and physically the backbone of a network. Inferior quality of network cabling results in network failures and in networks with unreliable performance. The equipment used to perform these tests involves certain electrical and mathematical concepts and terms, such as signal, wave, frequency, and noise. Understanding this vocabulary is helpful when learning about networking, cabling, and cable testing. This chapter corre- sponds to the Module 4 and 5 content from the CCNA 1 online curriculum. ■ Chapter 5, “Ethernet Fundamentals,” discusses the operation of Ethernet, Ethernet framing, error handling, and the different type of the collisions on Ethernet net- works. In addition, this chapter introduces the collision domains and broadcast domains. Finally, this chapter describes segmentation and the devices used to create the network segments. This chapter corresponds to the Module 6 content from the CCNA 1 online curriculum. ■ Chapter 6, “Ethernet Technologies and Ethernet Switching,” introduces Layer 2 bridging and switching techniques. It introduces the Spanning Tree Protocol (STP), tells how STP works, and covers the STP switch port states. This chapter corresponds to the Module 7 and 8 content from the CCNA 1 online curriculum. 1102.book Page xxix Tuesday, May 20, 2003 2:53 PM xxx ■ Chapter 7, “TCP/IP Protocol Suite and IP Addressing,” presents an overview of the TCP/IP protocol suite. It starts with the history and future of TCP/IP, com- pares the TCP/IP protocol model to the OSI model, and identifies and describes each layer of the TCP/IP protocol suite. This chapter corresponds to the Module 9 content from the CCNA 1 online curriculum. ■ Chapter 8, “Routing Fundamentals and Subnets,” covers the topics related to the Internet Protocol (IP). This chapter also discusses the difference between routing and routed protocols, and tells how routers track distance between locations. Finally, this chapter introduces the distance vector, link-state, and hybrid routing approaches, as well as how each resolves common routing problems. This chapter corresponds to the Module 10 content from the CCNA 1 online curriculum. ■ Chapter 9, “TCP/IP Transport and Application Layer,” covers the issues related to the transport layer and how it uses the services provided by the network layer, such as best path selection and logical addressing, to provide end-to-end commu- nication between source and destination. This chapter describes how the trans- port layer regulates the flow of information from source to destination reliably and accurately. This chapter corresponds to the Module 11 content from the CCNA 1 online curriculum. ■ Chapter 10, “WANs and Routers,” introduces WAN devices, technologies, and standards. In addition, it discusses the function of a router in a WAN. This chap- ter corresponds to the Module 1 content from the CCNA 2 online curriculum. ■ Chapter 11, “ Router Fundamentals,” describes how to start a router for the first time by using the correct commands and startup sequence to do an initial config- uration of the router. This chapter also explains the startup sequence of a router and the setup dialog that the router uses to create an initial configuration file using current versions of Cisco IOS Software. This chapter corresponds to the Module 2 content from the CCNA 2 online curriculum. ■ Chapter 12, “Router Configuration,” discusses the router modes and configura- tion methods for updating a router’s configuration file. It is important that a firm understand Cisco IOS Software and know the procedures for starting a router. In addition, this chapter describes the tasks necessary for password recovery. This chapter corresponds to the Module 3 content from the CCNA 2 online curriculum. ■ Chapter 13, “Learning About Neighboring and Remote Devices,” covers how to implement, monitor, and maintain Cisco Discovery Protocol by using the correct router commands. In addition, this chapter explains the three most used commands. This chapter corresponds to the Module 4 content from the CCNA 2 online curriculum. 1102.book Page xxx Tuesday, May 20, 2003 2:53 PM . Module 1 content from the CCNA 1 online curriculum. 11 02. book Page xxviii Tuesday, May 20 , 20 03 2: 53 PM xxix ■ Chapter 2, Networking Fundamentals,” introduces some of the terminology used by networking. .979 Appendix C Check Your Understanding Answer Key. . . . . . . . . . . . . . . . . .10 09 Index 10 47 11 02. book Page xxii Tuesday, May 20 , 20 03 2: 53 PM xxiii Cisco Systems Networking Icon Legend Cisco. corresponds to the Module 7 and 8 content from the CCNA 1 online curriculum. 11 02. book Page xxix Tuesday, May 20 , 20 03 2: 53 PM xxx ■ Chapter 7, “TCP/IP Protocol Suite and IP Addressing,” presents