This is correct - the primary benefit of multi-hop in most topologies would be on a downstream iBGP speaker to (for example, a core facing route-reflector) with equal IGP costs to each edge router - this would achieve proper outbound load balancing. Also worth noting is that this will only be useful if Peter continues to use a single provider for his multiple sessions. If, one day Peter decides to bring in a second carrier for redundancy purposes multi-path will no longer load balance since as-path's will now be different. There is a hidden IOS command in newer releases to get around this: bgp bestpath as-path multipath-relax that will permit multi-path table installation of identical routes ignoring the as-paths attribute. As you continue to add diverse upstreams in multiple locations however, this will not scale too well. Eventually you will need to start doing some traffic engineering via as-path + local-pref or other method to nail-down upstream route preferencing if you want to meet commits on all these diverse ports.
Cheers, Kevin Hodle On Thu, May 21, 2009 at 9:27 AM, Pete Templin <[email protected]> wrote: > Phil Mayers wrote: > >> I'm not 100% certain about this, but my understanding is that there is >> still only 1 FIB entry for the route; it just has >1 next hop. >> >> However - will this work? For eBGP-multipath, the paths have to be >> basically identical except next-hop. This won't be the case, since each >> router will prefer its direct link (lower IGP cost). > > I think you're close: rule #7 says "Prefer eBGP over iBGP paths", so each > router will prefer its direct link (since it's external). The indirect > paths won't be available for parallel path selection since they've fallen > out before the bottom. > > pt > > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > -- || Kevin Hodle || || 913-780-3959 (Primary) || 913-626-7197 (Mobile) PGP KeyID [0xBBDE8ED7] fingerprint [3E1B 1F10 938E A831 8CF2 670C 1329 0B8B BBDE 8ED7] _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
