Cisco routers are used widely both on the Internet and in corporate intranets. At the same time, the Cisco Internet Operating System (IOS) has grown to be very large and complex, and Cisco documentation fills several volumes. Cisco IOS Access Lists focuses on a critical aspect of the Cisco IOS--access lists. Access lists are central to the task of securing routers and networks, and administrators cannot implement access control policies or traffic routing policies without them. Access lists are used to specify both the targets of network policies and the policies themselves. They specify packet filtering for firewalls all over the Internet. Cisco IOS Access Lists covers three critical areas: *Intranets. The book serves as an introduction and a reference for network engineers implementing routing policies within intranet networking. * *Firewalls. The book is a supplement and companion reference to books such as Brent Chapman's Building Internet Firewalls. Packet filtering is an integral part of many firewall architectures, and Cisco IOS Access Lists describes common packet filtering tasks and provides a ''bag of tricks'' for firewall implementers. *The Internet.This book is also a guide to the complicated world of route maps. Route maps are an arcane BGP construct necessary to make high level routing work on the Internet. Cisco IOS Access Lists differs from other Cisco router titles in that it focuses on practical instructions for setting router access policies. The details of interfaces and routing protocol settings are not discussed.