Communities BCP [was: RE: BGP Path Filtering]

Jay Ford jay-ford at
Fri May 16 19:26:38 UTC 2003

On Fri, 16 May 2003, Joe Abley wrote:
> Examples of characteristics I have seen in the wild are:
>   + I was learnt from a peer
>   + I was learnt from a transit provider
>   + I was learnt from a customer
>   + I was learnt over an exchange point
>   + I was learnt over a private peering connection
> These are all markers to be used in setting internal policy, so the
> choice of numbers really doesn't matter. You can add or remove
> characteristics from your list when necessary without having to
> renumber anything. You can (and probably should) strip all these
> attributes before sending routes to EBGP peers, so nobody else has to
> see them.

You can & definitely should strip those community values on announcements you
receive from EBGP peers.  Interesting things happen if you let others turn
your routing policy knobs when you think they can't reach them.

Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford at, phone: 319-335-5555, fax: 319-335-2951

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