Routing and WAN connections / Border Gateway Protocol version 4 (BGPv4) |
"Community" is an optional BGP attribute that can be used to identify prefixes and collect them into logical groups. Inbound and outbound policies can be applied to these groups. It is possible to specify multiple communities for a single prefix.
In addition to the well-known communities NO-ADVERTISE or NO-EXPORT, the meaning of a community can be freely defined by the provider. So for example, the provider of AS "64500" specifies that customer routes with the community "64500:200" are to be treated with preference "200", and routes with the community "64500:90" are to be treated with the preference "90".
The following example shows how the community "64500:200" is added to all outbound routes.