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BGP communities allow you to group a set of IP addresses and apply routing decisions based on the identity of the group or community.
To implement this feature, map a set of communities to certain BGP local preference values. Then you can apply a uniform BGP configuration to the community as a whole as opposed to each router within the community. The routers in the community can capture routes that match their community values.
Use community attributes to can configure your BGP speaker to set, append, or modify the community of a route that controls which routing information is accepted, preferred, or distributed to other neighbors. The following table displays some special community attributes that a BGP speaker can apply.
Community attribute |
Description |
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Not advertised outside a BGP confederation boundary. A Standalone autonomous system that is not part of a confederation should be considered a confederation itself. |
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Not advertised to other BGP peers. |
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Not advertised to external BGP peers. This includes peers in other members’ autonomous systems inside a BGP confederation. |
For more about communities, see RFC 1997 and RFC 1998.
