bgp community number

Answered Question
Sep 21st, 2007
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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?




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Correct Answer by Pavel Bykov about 9 years 7 months ago

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.

Correct Answer by Richard Burts about 9 years 7 months ago

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

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Correct Answer
Richard Burts Fri, 09/21/2007 - 10:36
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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

Correct Answer
Pavel Bykov Fri, 09/21/2007 - 10:39
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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 Fri, 09/21/2007 - 10:39
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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,

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