Introduction
The Internet economy has played a significant part in the world economy since the mid 1990s. For many years prior, the Internet was the domain of U.S. academic research and defense internetworking, and a few entrepreneurs around the world who believed that a TCP/IP-based wide-area network (WAN) would be a viable alternative to the private wire networks that businesses were using to communicate with each other. The many ISP engineers who learned their skills in that period look on those early pioneering days at the end of the 1980s and early 1990s as something special. Work was invariably hard, and technology challenges were seemingly insurmountable when compared with the relative ease of use and configuration these days. But the sense of competition was more a friendly rivalry and partnership to make the fledgling Internet a fun place to be.
This pioneering spirit, and the desire of the Internet community to make the Internet a success, has resulted in the Internet becoming the major part of our lives at the start of the 21st century. It's now a huge commercial network, very competitive, with many players, small and large, from all over the world, heavily involved in its infrastructure. More people are taking part in the Internet every day, both end users with their first computer connecting to the World Wide Web, and new ISPs anxious to become part of a very significant growth industry. Furthermore, the few remaining countries in the world without an Internet connection are investigating connecting up and examining the advantages being networked will offer their local economies.
As the Internet has grown in our day-to-day consciousness, so have textbooks aspiring to help newcomers find the proverbial pot of gold: books ranging from beginner guides to designing web pages, to explaining what the Internet is, to describing the business process, to becoming a successful ISP. However, there has been precious little that describes the configuration concepts and tricks of the trade that ISP network engineers use in their daily lives—there is an argument which says, "We have been too busy fixing the potholes in the Internet superhighway to actually spend time writing down what we do."
Motivation
The inspiration for this book has come from three sources. The first is Cisco IOS Software. Cisco has been part of the Internet since the Internet started, building one of the first devices to move IP packets across a WAN. Over the years, IOS has grown from being a fairly basic piece of software to a highly sophisticated, feature rich, and extremely powerful router control suite. A tremendous range of features has been built into the IOS. This extensive feature set is excellent for public network ISPs, giving their network engineers a large number of options and capabilities that can be designed into the network.
While a huge number of features may be desirable, IOS also poses a problem— network engineers busy running their networks have a difficult time keeping up with all the new IOS features. Many engineers, even experienced network engineers, do not know how, when, and where to deploy the various features in their network.
This book highlights many of the key IOS features in everyday use in the major ISP backbones of the world. Judicious study and implementation of the IOS pearls contained in this book will help to prevent problems, increase security, improve performance, and ensure the operational stability of the Internet.
The second source of inspiration for writing this book is that there is no complete reference text for newcomers to the industry to take router products and build an ISP network from them. There is a great deal of documentation about network design practices, discussing ISP business practices, configuring the various routing protocols, and all the higher level services that ride on the Internet. Such texts as Internet Routing Architectures, Second Edition, and the ISP Survival Guide have helped many ISPs deal with scaling their backbones and getting the most from their ISP businesses. But when a newcomer is faced with a blue/green metal cased box fresh out of its packing box, a CD-ROM with all the documentation for this piece of equipment, there is the sinking feeling of "what happens now?" The intention of this book is to guide both newcomers and experienced network engineers through the optimal configuration of that blue/green box and its parent network, to integrate it effectively and securely into an ISP network, and to be part of the Internet backbone.
The final source of inspiration has already been touched on in this introduction: We all have been too busy working to write down what we are doing. Our daily working lives include outreach to new providers, helping existing providers make their networks better, and so on. There is much repetition of concepts which are obvious, but not documented in a general text. The "IOS Essentials Whitepaper" started this all off, documenting special Cisco IOS features that were in use almost exclusively in the ISP industry. Many friends and colleagues in the industry have encouraged us to write a book based around the whitepaper, putting our experiences and knowledge gained in the industry since the early 1990s down on paper so that others can benefit.
Intended Audience
The recommendations we make in this book focus on ISPs. The recommendations are not intended for other types of networks, whether private Internets or enterprise networks connecting to the Internet, although we are sure that some of the ideas and suggestions we make here could be applied successfully to such networks as well.
Engineers working for ISPs will benefit most from this text. (All engineers will benefit, be they engineers working in the ISPs Network Operations Center, working in the Customer Help Desk, or working on the core backbone itself.) All branches of an ISP engineering function will be exposed to the issues and concepts covered in this book, and we hope that this will be a valuable reference for everyone. The final chapter also has some relevance to the more business-orientated side of the ISP. Quite often, in our experience, planning a network is not treated quite as seriously as it should be. Planning is a joint effort between network engineers and business managers to ensure the best compromise between network design and the funding available to pay for it.
Organization
There are five chapters as well as several appendixes aimed to give the reader further information, tips, and templates relating to what has been covered in the paper. These chapters cover the following topics:
Chapter 1: Software and Router Management: Introduces the reader to Cisco IOS, the image trains designed specifically for ISPs, and how to manage these on the router. This chapter also covers router management, including configuration management, the command-line interface, and handling the status information, which the router can make available to its operators.
Chapter 2: General Features: Introduces the various miscellaneous features an ISP requires to organize on the router prior to dealing with routing protocols and network security. These features include the loopback interface, interface configuration good practices, CEF, and NetFlow.
Chapter 3: Routing Protocols: Covers the major issues facing ISPs with the configuration and feature set available with the major routing protocols. These include HSRP, IGP design, and the extensive feature set now available with the BGP implementation in Cisco IOS.
Chapter 4: Security: Covers the current major security features and support on the router, and gives an extensive discussion on the feature set available for defeating DoS attacks, which are so prevalent on the Internet today. Topics covered include router access, routing protocol security, and network security. Features discussed include applications of Unicast RPF and CAR.
Chapter 5: Operational Practices: The final chapter covers how the previous four chapters mesh together to help build an ISP backbone. The text concentrates on working through the typical processes used for building an ISP backbone, all the way from network design and layout, to positioning and implementing higher level services.
Appendixes: The appendixes provide additional reference material or examples to supplement the content of each chapter. Included here are route flap damping configurations, an extensive list of popular network management and monitoring tools in use, plus a working sample configuration of a simple ISP network using the IOS principles covered in this book.
The book is best read in order, because each chapter assumes knowledge of the content covered in previous chapters. Experienced engineers might be quite happy dipping into the text as they see fit. The style of the book is intended to allow both experts and beginners to feel at ease with the content.
Further Information
This book does not set out to summarize the rather copious documentation and other excellent materials Cisco has made available to the general public as well as to its customers. The book is based upon the "IOS Essentials Whitepaper," where we have collected preliminary documentation of features as they are released, or we have written our own explanation, as no documentation existed at all. Quite often Cisco's own documentation has followed much later than its first appearance in "IOS Essentials."
Along with this book, the authors are maintaining a web site with whitepaper updates to the contents of this book— http://www.ispbook.cOT. The web site http://www.cisco.com/public/cons/isp also contains other reference materials that may be useful for ISPs.
Where topics are not apparently covered in sufficient technical depth, the reader is encouraged to consult the following reference sources:
• Cisco System's Documentation (available to the general public on Cisco's website at http://www.cisco.com/univercd/) or on the CD-ROM that comes with each router.
• Local Cisco Systems' support channels.
• Public discussion lists. The list that focuses specifically on ISPs that use Cisco Systems equipment is cisco-nsp hosted by Jared Mauch. cisco-nsp is a mailing list which has been created specifically for ISPs to discuss Cisco Systems products and their use. To subscribe, send an e-mail to: [email protected] with a message body containing: subscribe cisco-nsp
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