Generating a local BGP default-route triggered by BGP Communities

dcarlson · ‎02-12-2007

I would like the ability to conditionally control the announcement of my local default-route generated by my internet edge routers (back to the core) by matching any routes received with the following BGP communities applied:

I would like to classify traffic coming in from our ISP using these two communities.

ABCDE:1239 (ISP AS only)

ABCDE:1 (All other AS's)

Is it possible to conditionally control a locally generated default-route by doing the following:

if bgp table has entries no entries for any bgp communities or only bgp community ABCDE:1239,

then do not send default-route to the core.

else

if bgp table has entries for communities ABCDE:1239 and ABCDE:1,

then send default-route to the core.

Since this is a not a default route that I am receiving from my ISP, but is one that I am generating locally, I am not sure how I can trigger a default route by matching a condition of received BGP communities (rather than a default route or less specific route).

Before going any further, I was wondering if this is even possible to do, since I haven't been able to make it work successfully so far.

sundar.palaniappan · ‎02-12-2007

I highly doubt conditional route injection based on community match exists and AFAIK, it's done based only on prefixes. A quick search on CCO seems to indicate that's the case. Someone from Cisco might be able to confirm this and even if the support for it isn't available now whether they intend to introduce this feature in the future releases.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a008056c866.html

HTH

Sundar