Cisco Router Configuration, Second Edition

Configuring IP Filtering via Access Lists

Since the first time that multiple systems were connected to form a network, there has been a need to restrict access to some systems or portions of a network for security, privacy, and other reasons. By using the packet-filtering facilities of the Cisco IOS software, a network administrator can restrict access to certain systems, network segments, ranges of addresses, and services based on a variety of criteria. The capability to restrict access is increasingly important as a company's network begins to connect to other outside networks, such as partner companies and the Internet.

The packet-filtering capabilities of the IOS software IP access lists allow for restricting packet flow based on the following ...