Configuring Prefix Lists for BGP and OSPF

Prefix lists allow you to permit or deny host IP addresses from route distribution in BGP and OSPF configurations. To configure prefix lists for BGP, this example assumes that you have a vRouter configured for BGP, vrouter-bgp, and you want to deny the IP address, 172.26.0.0 with the netmask 255.255.0.0, sequence number 5, and minimum prefix length 17 bits:

CLI (network-admin@Leaf1) > vrouter-prefix-list-add vrouter-name vrouter-bgp name deny-bits action deny prefix 172.26.0.0 netmask 255.255.0.0 seq 5 min-prefix-len 17

This prefix list rejects any subnets of 172.26.0.0/16 with prefixes 17 bits or longer. For example, the subnets 172.26.16.9/30 and 172.26.101.0/24 are rejected from route distribution.

The sequence number allows you to insert or remove new lines in a prefix list as well as at the beginning or end. It is recommended that you increment the sequence numbers by 10 so you can easily add or subtract lists from the configuration. See also:

• Configuring Open Shortest Path First (OSPF)
• Configuring BGP on a vRouter