8.3.3.8 - Force10 Networks

The following rules apply to prefix lists:
• A prefix list without any permit or deny filters allows all routes.
• An “implicit deny” is assumed (that is, the route is dropped) for all route prefixes that do not match a
permit or deny filter in a configured prefix list.
• Once a route matches a filter, the filter’s action is applied. No additional filters are applied to the route.
Implementation Information
In FTOS, prefix lists are used in processing routes for routing protocols (for example, RIP, OSPF, and
BGP).
Note: The S-Series platform does not support all protocols. It is important to know which protocol you are
supporting prior to implementing Prefix-Lists.
Configuration Task List for Prefix Lists
To configure a prefix list, you must use commands in the PREFIX LIST, the ROUTER RIP, ROUTER
OSPF, and ROUTER BGP modes. Basically, you create the prefix list in the PREFIX LIST mode, and
assign that list to commands in the ROUTER RIP, ROUTER OSPF and ROUTER BGP modes.
The following list includes the configuration tasks for prefix lists:
• Configure a prefix list on page 123
• Use a prefix list for route redistribution on page 126
For a complete listing of all commands related to prefix lists, refer to the FTOS Command Line Interface
Reference document.
Configure a prefix list
To configure a prefix list, use these commands in the following sequence, starting in the
CONFIGURATION mode:
Step Command Syntax Command Mode Purpose
1 ip prefix-list prefix-name CONFIGURATION Create a prefix list and assign it a unique
name.
You are in the PREFIX LIST mode.
2 seq sequence-number {deny |
permit} ip-prefix [ge
min-prefix-length] [le
max-prefix-length]
CONFIG-NPREFIXL Create a prefix list with a sequence number
and a deny or permit action. The optional
parameters are:
• ge min-prefix-length: is the minimum
prefix length to be matched (0 to 32).
• le max-prefix-length: is the maximum
prefix length to be matched (0 to 32).
Access Control Lists (ACL), Prefix Lists, and Route-maps | 123