9.2
BGP Route Filtering and Policy Routing
9.2.4 The ip prefix-list command

You can use prefix lists as an alternative to access lists with many BGP route-filtering commands. The advantages of using prefix lists rather than access lists include the following:

  • Significant performance improvement in loading and route lookup of large lists.
  • Support for incremental updates. Filtering via extended access lists does not support incremental updates.
  • A more user-friendly command-line interface.
  • Greater flexibility.

You must define a prefix list before you can apply it as a route filter. The Cisco IOS allows a very flexible configuration procedure, where each statement can be assigned its own sequence numbers.

To define a prefix list, use the ip prefix-list command, which has the syntax shown in Figure . Figure describes the parameters that are used with this command.