Ben Black wrote (on Oct 12):
perhaps i should have said "using iBGP as the only IGP" to avoid a flood of pedantic replies.
Without wanting to descend into a spiralling thread on this... It is perfectly acceptable to run iBGP as the sole IGP simply because in some situations there is not enouigh scope to run a more dynamic IGP of any other nature. One routing protocol uses less CPU/memory than two.
Just because BGP is your hammer doesn't mean every problem is a nail.
All BGP isn't good at is metrics. It makes it a very clumsy IGP, but useful in small-scale situations, like upto one or two site networks. But since I'm apparently off-topic. :-) I would agree with a previous poster that the majority of reasonably sized networks these days use OSPF as the IGP for both internal routes and, notably, next hops for use by BGP (in either Internal or External contexts). This is what we do. However, I know of three large networks in Europe that do use BGP as their sole IGP and I know of one other that is considering ditching OSPF and moving to BGP (they have bandwidth coming our of their ears so don't care about the granularity cost-metric gives you) because the CPU overhead of OSPF was too large for their network. Plenty of bandwidth but tight purse strings when it comes to hardware. Chris. -- == chris@easynet.net, chrisy@flix.net, chrisy@flirble.org == Systems Manager for Easynet, part of Easynet Group PLC.