Thursday, 7 August 2008

ip bgp-community new-format

Hmm today I discovered another command I did not really know about and probably should have. The ip bgp-community new-format command. After looking it up on the Cisco website I found the following:

To display BGP communities in the format AA:NN (AS-community number/2-byte number), use the ip bgp-community new-format command in global configuration mode.To re-enable the previous display format for BGP communities (NN:AA), use the no form of this command.

ip bgp-community new-format

no ip bgp-community new-format

Usage Guidelines

RFC 1997, BGP Communities Attribute specifies that a BGP community is made up of two parts that are 2 bytes long. The first part is the autonomous system number and the second part is a 2-byte number. In the most recent version of the RFC, a community is of the form AA:NN. The Cisco default community format is one 32-bit number. The ip bgp-community new-format command changes the community format to AA:NN to conform to RFC 1997.


The following example upgrades a router that uses the 32-bit number community format to the AA:NN format:

Router(config)# ip bgp-community new-format 

The following example shows how BGP community numbers are displayed when the ip bgp-community new-format command is enabled:

Router# show ip bgp
BGP routing table entry for, version 4
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
  35 from (
      Origin incomplete, metric 10, localpref 100, valid, external
      Community: 1:1
  Local from (
      Origin incomplete, metric 0, localpref 100, weight 32768, valid, sourced, best 

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