Prefix Lists and Prefix Trees

The user can create prefix lists or prefix trees and configure routemaps to allow or reject the lists.

List

Description

Prefix List

Simulate a sequential lookup and return the first matched entry as the true match.

Prefix list name:

  • Can be up to 16 characters in length

  • Can contain only letters, numbers, '-', '_', or '.'

Prefix Tree

Return the longest match as the true match.

Prefix List Syntax

set prefix-list <Name of Prefix List>

      sequence-number <1-4294967295>

            prefix <IP Address>/<Mask Length>

                     all [restrict {off | on}]

                     between <Start Mask Length> and <End Mask Length> [restrict {off | on}]

                     exact [restrict {off | on}]

                     refines [restrict {off | on}]

set prefix-list <Name of Prefix List> sequence-number <1-4294967295> off

set prefix-list <Name of Prefix List> off

Configure a prefix list called non-local to restrict prefixes 192.168.0.0/16, 10.0.0.0/8, and 172.16.0.0/12, but allow all other IPv4 prefixes:

set prefix-list non-local sequence-number 5 prefix 10.0.0.0/8 all restrict on

set prefix-list non-local sequence-number 10 prefix 192.168.0.0/16 all restrict on

set prefix-list non-local sequence-number 15 prefix 172.16.0.0/12 all restrict on

set prefix-list non-local sequence-number 20 prefix 0.0.0.0/0 all

Configure a prefix-list called "no-5-net" to restrict prefix 5.0.0.0/8 but allow all other /8 prefixes.

Any other prefixes will not be matched by this list (and therefore will be restricted unless another prefix list matches them):

set prefix-list no-5-net sequence-number 1 prefix 5.0.0.0/8 exact restrict on

set prefix-list no-5-net sequence-number 2 prefix 0.0.0.0/0 between 8 and 8

Prefix Tree Syntax

set prefix-tree <Name of Prefix Tree>

      prefix <IP Address>/<Mask Length>

            all [restrict {off | on}]

            between <Start Mask Length> and <End Mask Length> [restrict {off | on}]

            exact [restrict {off | on}]

            refines [restrict {off | on}]

set prefix-tree <Name of Prefix Tree> prefix <IP Address>/<Mask Length> off

set prefix-tree <Name of Prefix Tree> off

Configure a prefix tree called non-local to restrict all prefixes with mask lengths, which are shorter than or equal to /8, 192.168.0.0/16, and 172.16.0.0/12, but allow all other IPv4 prefixes:

set prefix-tree non-local prefix 0.0.0.0/0 between 0 and 8 restrict on

set prefix-tree non-local prefix 0.0.0.0/0 between 9 and 32

set prefix-tree non-local prefix 192.168.0.0/16 all restrict on

set prefix-tree non-local prefix 172.16.0.0/12 all restrict on

Configure a prefix tree named "10-net" to allow 10.1.1.0/24, restrict all sub-prefixes of 10.1.0.0/16, and allow all sub-prefixes of 10.0.0.0/8, except 10.0.0.0/8 itself.

Any other prefixes will not be matched by this list (and thus will be restricted unless another prefix tree matches them):

set prefix-tree 10-net prefix 10.0.0.0/8 refines

set prefix-tree 10-net prefix 10.1.0.0/16 all restrict

set prefix-tree 10-net prefix 10.1.1.0/24 exact