Reference Guide

Open Shortest Path First (OSPFv2 and OSPFv3) | 509
Filter routes
To filter routes, use prefix lists. OSPF applies prefix lists to incoming or outgoing routes. Incoming routes
must meet the conditions of the prefix lists, and if they do not, OSPF does not add the route to the routing
table. Configure the prefix list in CONFIGURATION PREFIX LIST mode prior to assigning it to the
OSPF process.
For configuration information on prefix lists, refer to IP Access Control Lists, Prefix Lists, and
Route-maps chapter in the FTOS Configuration Guide.
Use the following commands in CONFIGURATION-ROUTER OSPF mode to apply prefix lists to
incoming or outgoing OSPF routes
Command Syntax Command Mode Usage
ip prefix-list prefix-name CONFIGURATION
Create a prefix list and assign it a unique
name. You are in PREFIX LIST mode.
seq sequence-number {deny |permit} ip-prefix
[ge min-prefix-length] [le max-prefix-length]
CONFIG- PREFIX
LIST
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).
Command Syntax Command Mode Usage
distribute-list prefix-list-name in [interface] CONFIG-ROUTER-
OSPF-id
Apply a configured prefix list to incoming
OSPF routes.
distribute-list prefix-list-name out [connected |
isis | rip | static]
CONFIG-ROUTER-
OSPF-id
Assign a configured prefix list to outgoing
OSPF routes.