Routing is an essential element of all but the smallest data communications networks. At one level, routing and the configuration of routers are quite simple. But as networks grow in size and complexity, routing issues can become at once both large and subtle. Perversely, perhaps, we are grateful for the difficult problems large-scale routing can present—as network systems consultants, these problems are our bread and butter. Without them, the phrase “You want fries with that?” could be an unfortunate part of our daily vocabulary.
Cisco Certified Internetwork Experts are widely recognized for their ability to design, troubleshoot, and manage large networks. This recognition comes from the fact that you cannot become a CCIE by attending a few classes and then regurgitating some memorized facts onto a written test. A CCIE has proven expertise in an intense, famously difficult hands-on lab exam.
This book is the first of two volumes that focuses on TCP/IP routing issues. Early in the writing of the first edition, Kim Lew, former Cisco Systems program manager, said, “Our objective is to make CCIEs, not to make people who can pass the CCIE lab.” We entirely agree with that statement and have used it as a guiding principle throughout the writing of this book. Although the book includes many case studies and exercises to help you prepare for the CCIE lab, my primary objective is to increase your understanding of IP routing—both on a generic level and as it is implemented on Cisco routers.
The audience for this book is any network designer, administrator, or engineer who needs a full understanding of the interior routing protocols of TCP/IP. Although the practical aspects of the book focus on the Cisco IOS, the information is applicable to any routing platform.
The book is not only for readers who plan to become CCIEs, but for people who wish to advance their knowledge of TCP/IP routing. These readers will fall into one of three categories:
The “beginners” who have some basic networking knowledge and wish to begin a deep study of networking.
The intermediate-level networking professionals who have experience with routers, Cisco or otherwise, and plan to advance that experience to the expert level.
The highly experienced networking experts. These individuals have extensive hands-on expertise with Cisco routers and are ready to take the CCIE lab; however, they want a structured review and series of exercises for verification and validation.
CCIE Professional Development: Routing TCP/IP, Volume I focuses primarily on intermediate-level networking professionals while offering to beginners a structured outline of fundamental information and to experts the required challenges to hone their skills.
There are several factors influencing the changes contained in this second edition. The first factor is the CCIE itself. When I (Jeff) wrote the first edition of this book, the CCIE—specifically what is now called the Routing and Switching specialty of the CCIE—was the only certification Cisco Systems offered. Now, there is a series of certifications creating a path to the CCIE at the pinnacle. Moreover, the typical networking professional is more knowledgeable than in 1997. Given this, we have eliminated the first chapter of the original book, which covered such very basic concepts as the definition of bridges and routers and network addresses. (When was the last time you even saw a bridge in a network?)
The second factor influencing the changes in this edition is the changes in the Cisco Systems IOS. IGRP, which was frequently used when the first edition was written, is now a legacy protocol whose main significance is as the ancestor of EIGRP. Therefore the IGRP chapter of the first edition has been eliminated and IGRP is covered for historical perspective early in the EIGRP chapter. The IOS command suite itself has expanded to accommodate new functions and options; we have made every effort to include the commands and protocol extensions that did not exist in the late 1990s.
Lastly, a protocol that existed mostly only in proposal form in 1997—IPv6—is now in the early stages of worldwide deployment. You can expect to need a detailed knowledge of this protocol and the extensions to IP routing protocols that support it in the near future, if not already, so this second edition delves deeply into routing IPv6.
Other changes in this edition are semantic. For example, in the first edition, I (Jeff) made a point of differentiating between a “network” as a data link and an “internetwork” as a set of networks connected by routers. Although that terminology is certainly accurate, it is clumsy, and “internetwork” is seldom used these days. Instead, “network” usually refers to everything from a local link to worldwide autonomous systems operated by the likes of Level 3, NTT, and Sprint. We have attempted to bring the terminology in this edition up to modern, common usage.
The 14 chapters of the book are divided into three parts.
Part I, “Routing Basics,” examines the basics of IPv4 and IPv6, and the basics of routing. Although more advanced readers may wish to skip the first chapter, we recommend that they at least skim Chapter 3, “Static Routing,” and Chapter 4, “Dynamic Routing Protocols.” And, of course, if you are not yet familiar with IPv6, Chapter 2, “IPv6 Overview,” is a must-read.
Part II, “Interior Routing Protocols,” covers the IP Interior Gateway Protocols. Each protocol-specific chapter begins with a discussion of the theory, mechanics, and parameters of the protocol. This general overview is followed by case studies on configuring and troubleshooting the protocol using Cisco Systems’ IOS in various network topologies.
The Exterior Gateway Protocol, BGP, and topics such as multicast routing, Quality of Service, router security and management, and Network Address Translation, are covered in “Routing TCP/IP, Volume II.”
Part III, “Route Control and Interoperability,” examines the tools available for creating and managing interoperability with multiple IP routing protocols, and also such tools as default routes and route filtering. As such, the chapters of this last part provide an introduction to the tools necessary for building the complex routing policies introduced in Volume II. These chapters, like the ones in Part II, begin with concepts and conclude with case studies.
Most chapters conclude with a set of review questions, configuration exercises, and troubleshooting exercises. The review questions focus on the theoretical aspects of the chapter topic, whereas the configuration and troubleshooting exercises address Cisco-specific aspects of the chapter topic.
Also at the end of each chapter is a table with a brief description of all important Cisco IOS commands used in that chapter. The conventions used to present these commands are the same conventions used in the IOS Command Reference and presented earlier in this introduction.