Cisco IOS Cookbook, 2nd Edition

Preface

Cicso routers are nearly ubiquitous in IP networks. They are extremely flexible and reliable devices. The number and variety of features grows with each new release of the Internetwork Operating System (IOS). And while Cisco Press and several other publishers supply excellent documentation of these features both online and in a variety of books, it is often difficult to know when, why, and how to use these features. There are often many different ways to solve any given networking problem using Cisco devices. Some of these solutions are clearly more effective than others.

The most pressing question in the mind of you, the network engineer, is which of the many potential solutions is the most appropriate for your particular situation. And once you have decided to use a particular feature, the next question is how to actually implement it. Unfortunately, the feature documentation that describes a particular command or feature frequently does very little to answer either of these questions.

Indeed, there are many cases in which the Cisco IOS and documentation offers solutions that will make the network extremely difficult to support in the long term. These solutions are legitimate in odd special situations, but we strongly believe that they should be avoided in most production networks. In some cases this is because there are features that open potentially serious security holes in their default modes. In other cases, there are features that can render the network exceedingly ...