On Mon, Sep 02, 2002 at 11:16:51PM -0400, alex@yuriev.com wrote:
To carry the bgp next-hops around the network? You could add in statics for every next-hop on every router, but this kind of configuration is complex and prone to errors such as loops in relatively minor cases. statically routing every next-hop "does not scale". Not to mention that many of us like the "compare igp metric" portion of the BGP decision tree.
Rubbish again.
*Every* interface that you bring up has a connected route. You redistribute those routes into IGP. You redistgribute statics from that router into IGP. Nail those routes into bgp and set internal community on it.
network xxx.yyy.zzz.www mask ppp.hhh.ooo.lll route-map set-igp-community.
So how does this provide equivalent functionality to "compare igp metric"? I think there are a lot of folks out there who might like to do the whole nearest-exit thing. Even if you went to the trouble of setting up route-maps to your heart's content and managed to get each router to prefer paths from the nearest exit router, it wouldn't do you much good when a link failure turns that "nearest" into "furthest" but the iBGP session stays up. I think maybe the word "need" is being taken a little too seriously here. No, you don't NEED a separate IGP to make BGP work. But then again, you don't NEED a lot of things to make a network go in its most basic form. However, without some of those "unnecessary" things you might not find it to perform quite to your liking either. For my network, I'd much rather deal with some extra SPF calculations than slow convergence and playing route map games to get things like nearest-exit working. Links and loopbacks => IGP Everything else => BGP But then, nobody ever accused any two engineers of having the same personal preferences... -c