I come to NANOG to get feedback from others who may be doing this. We have 3 upstream transit providers and PNI and public peers in 2 locations. It'd obviously be easy to transition to doing partial routes for just the peers, etc, but I'm not sure where to
draw the line on the transit providers. I've thought of straight preferencing one over another. I've thought of using BGP filtering and community magic to basically allow Transit AS + 1 additional AS (Transit direct customer) as specific routes, with summarization
to default for the rest. I'm sure there are other thoughts that I haven't had about this as well....
Hi James,
When I was at the DNC in 2007, we considered APNIC-region /8s lower priority than ARNI region (for obvious reasons) so I got some extra life out of our router by pinning most APNIC /8s to a few stable announcements, preferring one transit to the other with a fallback static route. This worked in the short term but I wouldn't want to do it as a long term solution.
As a more generic approach: filter distant (long AS path) routes because there's a higher probability that they're reachable from any transit with about the same efficiency.
Any time you summarize routes, you WILL lose connectivity during network partitions. Which defeats part of the purpose of having BGP with multiple transits. Partitions are rare but they can persist for days (*cough* cogent *cough*). So that's a risk you should plan for.
Regards,
Bill Herrin