On Sun, May 30, 2010 at 10:16:14AM -0700, Kevin Oberman wrote:
I remember a posting to this list back in the late 90s from Tony Li, who knows a bit about BGP. He urged that multi-hop BGP never be used and pointed out that it had not been intended for use except as a test tool, not a production one and should have been stripped from IOS before it was shipped.
While there are a few good cases for using it, it is generally a bad, bad idea. And this thread demonstrates that he had reason for the warning
I think you guys may be getting a tad carried away with the crusade against multihop BGP. The only thing you're really giving up when you use it is liveness detection, which as we all know BGP is actually pretty terrible at implementing anyways (hows that 180 sec IOS default working out for you?). There are much better mechanisms out there, like BFD, which could be used to provide better liveness detection to BGP through nexthop invalidation. I'm not saying everyone should run out and do all their peering over multihop EBGP without carefully considering a replacement for the liveness detection component, I just hate it when people get religious about such a simple concept for no good reason (well, other than Randy Bush getting to do his best Andy Rooney impersonation :P). Multihop BGP is no more evil than anything else we do with the Internet, and the fact that we've all managed to use it successfully for IBGP proves that it can work out just fine. There are some pretty interesting things you can accomplish as far as large scale traffic engineering if you can free yourself from the requirement of speaking EBGP with a directly connected neighbor, processed by whatever slow overpriced router CPU could be stuffed into that box. Again, I just hate to see the concepts dismissed out of hand because of some old BGP ideology about a problem that can be addressed any number of other ways. -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)