nanog mailing list archives
RE: AT&T NYC
From: "Derek Samford" <dsamford () fastduck net>
Date: Thu, 29 Aug 2002 16:48:47 -0400
Ralph, Okay, no one ever said an IBGP mesh was bad. We were all upset by the mention of an IGP distributed into an EGP. Let's do a little math here. The formula for IBGP sessions goes as follows. n*(n-1)/2 2=1 3=3 4=6 5=10 So you've only got 4 routers? That's fine, 6 sessions is not too hard to maintain. However, one more router, annd10 can get to be cumbersome and 10 Routers in your network, you have to maintain 45 BGP sessions. My personal favorite approach (And this may, or may not, start a religious war.) is confederations. The great part is, if your IBGP mesh inside a Sub-as gets to large, you can add a route-reflector, and have a hybrid RR/Confederation approach. This is very scalable, although there are some issues with being able to follow shortest path out of a confederation, so you need to have a little skill at traffic engineering. Building networks is easy Ralph, building SCALEABLE networks, is not. Derek
-----Original Message----- From: Ralph Doncaster [mailto:ralph () istop com] Sent: Thursday, August 29, 2002 4:44 PM To: Derek Samford Cc: 'Robert A. Hayden'; 'Michael Hallgren'; 'Peter van Dijk'; nanog () merit edu Subject: RE: AT&T NYC On Thu, 29 Aug 2002, Derek Samford wrote:I personally prefer using IS-IS for loopback/infrastructure routes,
and
I use confederations for my IBGP. If a confederation ever gets to
large,
I can always add a route-reflector inside the confederation. Ralph,
you
have never failed to amaze me with your love for WCP (Worst Current Practices.)OK, then hand me a clue and explain why ruing an iBGP mesh with 3-4 routers is so bad (seeing as Bassam Halabi didn't in his book). -Ralph
Current thread:
- routing architectures ( was Re: AT&T NYCrouting ), (continued)
- routing architectures ( was Re: AT&T NYCrouting ) Ralph Doncaster (Aug 29)
- Re: routing architectures ( was Re: AT&T NYCrouting ) Robert A. Hayden (Aug 29)
- RE: routing architectures ( was Re: AT&T NYCrouting ) Jason Lixfeld (Aug 29)
- RE: routing architectures ( was Re: AT&T NYCrouting ) Jason Lixfeld (Aug 29)
- Re: routing architectures ( was Re: AT&T NYCrouting ) Ross Chandler (Aug 29)
- Re: routing architectures ( was Re: AT&T NYCrouting ) Kurtis Lindqvist (Aug 30)
- RE: AT&T NYC Michael Hallgren (Aug 29)
- RE: AT&T NYC Robert A. Hayden (Aug 29)
- RE: AT&T NYC Derek Samford (Aug 29)
- RE: AT&T NYC Ralph Doncaster (Aug 29)
- RE: AT&T NYC Derek Samford (Aug 29)
- RE: AT&T NYC Ralph Doncaster (Aug 29)
- Re: AT&T NYC William Waites (Aug 29)
- RE: AT&T NYC Derek Samford (Aug 29)
- Re: AT&T NYC Mark Kent (Aug 29)
- RE: AT&T NYC Iljitsch van Beijnum (Aug 30)
- RE: AT&T NYC alex (Aug 30)
- RE: AT&T NYC Iljitsch van Beijnum (Aug 30)
- RE: AT&T NYC alex (Aug 30)
- RE: AT&T NYC Daniel Golding (Aug 29)
- RE: AT&T NYC Ralph Doncaster (Aug 29)