Cisco IOS is a powerful and complex operating system, with an equally complex configuration language. There are many commands, with many options, and if one thing is configured incorrectly, the entire company could find itself offline. This text covers IOS configuration for the TCP/IP protocol family. It is divided into two parts: the first part includes chapters on the user interface, configuring lines and interfaces, access lists, routing protocols, and dial-on-demand routing and security; the second part is a quick reference to all the commands that you need to work with TCP/IP, including the lower-level protocols on which it relies, and lots of examples of the most commonly encountered configuration steps for the routers themselves.