bgp community number

[cwangskr]

when I do a sh ip bgp community ? I get the following on two routers.

route-views.oregon-ix.net>sh ip bgp community ?

aa:nn community number

local-AS Do not send outside local AS (well-known community)

no-advertise Do not advertise to any peer (well-known community)

no-export Do not export to next AS (well-known community)

| Output modifiers

<cr>

jo100-r5>sh ip bgp comm

jo100-r5>sh ip bgp community ?

<1-4294967295> community number

local-AS Do not send outside local AS (well-known community)

no-advertise Do not advertise to any peer (well-known community)

no-export Do not export to next AS (well-known community)

| Output modifiers

<cr>

one router has a community number <1-4294967295> and the other one has aa:nn

what is the difference? Is it IOS feature?

[Richard Burts · Accepted solution]

Chandra

Yes it is an IOS feature. You can use the command ip bgp-community new-format to have the router format the community with the AS:value format.

HTH

Rick

[cwangskr]

Thanks, for the help

[Pavel Bykov · Accepted solution]

Yes, this is an IOS feature. The first router has what is called a "new format" of BGP community. They are both 32 bit numbers, but in "new format" the community is specified in "aa:nn" where "aa" is your AS number and "nn" is an arbitrary number. It was created for practival purposes, because 65000:1 was easier to write and manage than for example 3128683542.

To turn on or off the new format feature use "ip bgp-community new-format" global configuration command.

Hope this helps.

Please rate all helpful posts.

[Harold Ritter]

Chandrathilaka,

The following command is configured on the first but not on the second router:

R1(config)#ip bgp ?

new-format select aa:nn format for BGP community

Regards,