Introduction

The Internet, an upstart academic experiment in the late 1960s, struggles with identity and success today. From the ARPANET to the NSFnet to ANYBODYSNET, the Internet is no longer owned by a single entity; it is owned by anybody who can afford to buy space on it. Tens of millions of users are seeking connectivity, and tens of thousands of companies are feeling left out if they do not tap into the Internet. This has put network designers and administrators under a lot of pressure to keep up with networking and connectivity needs. Understanding networking, and especially routing, has become a necessity.

Some people are surprised when networks fail and melt down, but others are surprised when they don't. This seems to be the case because there is so little useful information out there. Much of the information on routing that has been available to designers and administrators up until now is doubly frustrating: The information makes you think you know how to build your network—until you try, and find out that you don't. The first edition of this book addressed real routing issues, using real scenarios, in a comprehensive and accessible way.

In addition to providing a thorough update to the original material, this edition introduces recent enhancements to the BGP protocol, discusses changes surrounding registration and allocation of Internet numbers, and provides additional information on research and educational networks.

Objectives

The purpose of this book is to make you an expert on integrating your network into the global Internet. By presenting practical addressing, routing, and connectivity issues both conceptually and in the context of practical scenarios, this book aims to foster your understanding of routing so that you can plan and implement major network designs in an objective and informed way. Whether you are a customer or a provider (or both) of Internet connectivity, this book anticipates and addresses the routing challenges facing your network.

Audience

This book is intended for any organization that might need to tap into the Internet. Whether you are becoming a service provider or are connecting to one, you will find all you need to integrate your network. The perspectives of network administrators, integrators, and architects are considered throughout this book. Even though this book addresses different levels of expertise, it progresses logically from the simplest to the most challenging concepts and problems, and its common denominator is straightforward, practical scenarios to which anyone can relate. No major background in routing or TCP/IP is required. Any basic or background knowledge needed to understand routing is developed as needed in text discussions, rather than assumed as part of the reader's repertoire.

Organization

The book is organized into four parts:

  • Part I: The Contemporary Internet— Chapters 1 through 3 cover essential introductory aspects of the contemporary Internet with respect to its structure, service providers, and addressing. Even if you are already familiar with the general structure of the Internet, you are encouraged to read the portions of Chapter 1 concerning Network Access Points, the Routing Arbiter Project, and Network Information Services. The pressures that precipitated these components of the Internet have continuing practical implications for routing design problems faced by administrators. Chapter 2 provides valuable criteria by which to evaluate Internet service providers. If you represent such a provider, or are already a customer of one, some of the information might be familiar to you already. Chapter 3 discusses classless interdomain routing (CIDR), VLSM (variable-length subnet masks), IPv6, and other aspects of Internet addressing.

  • Part II: Routing Protocol Basics— Chapters 4 and 5 cover the basics: properties of link-state and distance vector routing protocols and why interdomain routing protocols are needed and how they work. These topics are covered both generally and in the specific context of BGP (Border Gateway Protocol)—the de facto standard interdomain routing protocol used in the Internet today. BGP's particular capabilities and attributes are thoroughly introduced.

  • Part III: Effective Internet Routing Designs— Chapters 6 through 10 delve into the practical, design-oriented applications of BGP. The BGP attributes introduced in Part II are shown in action, in a variety of representative network scenarios. BGP's attributes are put to work in implementing design goals such as redundancy, symmetry, and load balancing. The challenges of making intradomain and interdomain routing work in harmony, managing growing or already-large systems, and maintaining stability are addressed.

  • Part IV: Internet Routing Device Configuration— Chapters 11 and 12 contain numerous code examples of BGP's attributes and of various routing policies. The code examples will make the most sense to you after you have read the earlier chapters, because many of them address multiple concepts and design goals. So that you can juxtapose textual discussions from earlier chapters with the code examples in Chapters 11 and 12, pointers called "Configuration Examples" appear in the earlier chapters. When you see one, you might want to fast-forward to the referenced page to see a configuration example of the attribute or policy being discussed.

Finally, several appendixes provide additional references for further reading, an up-to-date Cisco IOS™ BGP command reference, and information regarding IOS™ modifications intended to provide a more intuitive BGP command-line interface.

Approach

It is very hard to write about technical information in an accessible manner. Information that is stripped of too much technical detail loses its meaning, but complete and precise technical detail can overwhelm readers and obscure concepts. This book introduces technical detail gradually and in the context of practical scenarios whenever possible. The most heavily technical information—configuration examples in the Cisco IOS language—is withheld until the final two chapters of this book so that it is thoroughly grounded in the concepts and sample topologies that precede it.

Although your ultimate goal is to design and implement routing strategies, it is critical to grasp concepts and principles before applying them to your particular network. This book balances conceptual and practical perspectives by following a logical, gradual progression from general to specific, and from concepts to implementation. Even in chapters and sections that necessarily take a largely descriptive approach, hands-on interests are addressed through pointers to configuration examples, frequently asked questions, and scenario-based explanations.

The scenario-based approach is an especially important component of this book: it utilizes representative network topologies as a basis for illustrating almost every protocol attribute and routing policy discussed. Even though you might not see your exact network situation illustrated, the scenario is specific enough to facilitate learning by example, and general enough that you can extrapolate how the concepts illustrated apply to your situation.

Features and Text Conventions

This book works hard not to withhold protocol details and design-oriented information, while at the same time recognizing that building general and conceptual understanding necessarily comes first. Two features are included to help emphasize what is practical and design-oriented as underlying concepts are developed:

  • Pointers to configuration examples—Located close to pertinent text discussions, these references point forward to places in Chapters 11 and 12 where related configuration examples can be found.

  • Frequently Asked Questions—Located at the end of every chapter, these questions anticipate practical and design-oriented questions you might have, for your particular network, after having read the chapter.

Command Syntax Conventions

The conventions used to present command syntax in this book are the same conventions used in the IOS 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 n optional elements.

  • Boldface indicates commands and keywords that are entered literally as shown. In actual configuration examples and output (not general command syntax), boldface indicates commands that are manually input by the user (such as a show command).

  • Italics indicates arguments for which you supply actual values.

Icons Used in This Book

Throughout the book, you will see the following icons used for peripherals and other devices.

Throughout the book, you will see the following icons used for networks and network connections.

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
3.234.246.109