9.13 Prefix Lists

The traditional use of prefix lists was to filter routing updates. The traditional use of access-lists was for packet filtering, which was then extended to route filtering.

Prefix-lists are advantageous to access-lists in the following ways:

1. They are more versatile and can match on a larger number of routes than several access-list entries, because they match on prefix, mask, and provide mechanisms to match a range of prefixes using operators like “le” (less than or equal) and “ge” (greater than or equal).
2. They are processed in a tree structure, which is processed more efficiently by the network device than a traditional access-list.
3. They are not as cumbersome as extended ACLs to configure.

Note that the use of sequence numbers is available with prefix lists, but is not exclusive to it.