BGP Communities

Neil J. McRae neil at
Mon Nov 19 07:41:09 UTC 2007

Community lists and route maps but the place to start is a sheet of paper and to think about what your goal is. Its quite easy (especially on large networks) to build contradictory logic. Also beware what implications you have for cost and capacity. E.g. A customer could signal send all my traffic via $expensivetransit and you then lose money quick.

Communties are also good for blackhole signalling but remember your customers will raise queries when deploying them too!


-----Original Message-----
From: James Blessing <james.blessing at>
Sent: 19 November 2007 07:17
To: nanog at
Subject: BGP Communities


Following up on the thread about BGP communities, I was wondering if
there is a guide on how to actually implement communities within a

There are a couple of presentations about why communities are good and
about the general design of communities but my googlefu has so far not
found a "Here is how to deploy Communities" guide that takes into
account the important things like configuration maintenance, how to
scale and what mistakes not to make.

We are a Cisco house so any Cisco specific documentation would be great
but any guide right now would be a start.

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