BGP Community Attribute
Share this page:Community attribute is one of those non-standard BGP attributes that you really need to know well if you wish to use it. The big advantage is that from time to time you will just swoop in and solve a big architecture problem your colleague Network Engineers are having. The down side is that it’s a bit tacky. For example, these are the communities you can set within the route-map configuration>
Cisqueros_R1(config-route-map)#set community ?
** <1-4294967295> community number**
** aa:nn community number in aa:nn format**
** additive Add to the existing community**
** internet Internet (well-known community) <— ADVERTISE these networks**
** local-AS Do not send outside local AS (well-known community) <— ONLY advertise within the AS**
** no-advertise Do not advertise to any peer (well-known community) <— The neighbor will not advertise what was matched to neither eBGP nor iBGP neighbors**
** no-export Do not export to next AS (well-known community) <— Like previous, but ONLY for eBGP**
** none No community attribute**
**
*IMPORTANT: Do not forget to actually SEND the community to the neighbor, otherwise your configuration will not work!!!
** (config-router)#neighbor x.x.x.x send-community**
You can of course apply the BGP community attributes on the INBOUND and OUTBOUND direction, where you automatically override the existing value.
Besides these well-known community values, you can also assign a random community number and use them later as BGP TAGS.