BGP - Large BGP communities

Large BGP communities use what is known as a Large Community Attribute, which is a 12 byte vale divided into three fields of four bytes each. This is an extension to the more conventional 32-bit value used for BGP communities.

Similar in syntax to conventional communities, large BGP communities use the following syntax for the 12-byte community value:


where each of the values in the field are four bytes each.

An example of a route-policy matching a large community attribute and adjusting the local preference is shown below:

route-policy set-something if large-community matches-any (15562:4:3) then set local-preference 120 endif end-policy

Similarly, an example of a route-policy setting a particular large community attribute can be seen below:

route-policy set-something set large-community (15562:45:29) additive end-policy


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