IGPs in use

Chrisy Luke chrisy at flix.net
Tue Oct 13 14:57:10 UTC 1998


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 at easynet.net, chrisy at flix.net, chrisy at flirble.org
== Systems Manager for Easynet, part of Easynet Group PLC.



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