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Re: Not sure what I'm seeing... (Looking Glass Query)

  • From: Stephen J. Wilcox
  • Date: Fri Mar 29 04:44:22 2002

we see the cw route
  286 209 3561 19138

i think its looks okay.. as you know in bgp the shortest as path is chosen
first, and it is that which is propogated. i think what you might be
seeing is the fact that the cw routes are better as they are all shorter:

  7911 3561 19138
  5056 3561 19138
  1 3561 19138

the net vriginia ones all having an extra hop because net virginia
connects to sprint and then on from there:

  4006 1239 7066 19138
  6395 1239 7066 19138
  3549 1239 7066 19138

so as they go across the routers the net virginia ones tend to be filtered
out in preference to cw

why dont you try prepending an extra 19138 onto your announcement into cw,
that should even things up and then take another look at the routing


On Fri, 29 Mar 2002, Aaron Mahler wrote:

> Hello!
>    Hope nobody minds a quick question from a small, non-transit but BGP 
> aware AS...
>    Since the day we started using multiple circuits and BGP I've always 
> seen multiple paths through each of our providers to our network (AS 
> 19138). At least a few C&W (3561) and at least a few Network Virginia 
> (7066) via Sprint...
>    For weeks or more now, every single looking glass save one shows - 
> for the most part - a single advertised path through C&W. No sign of 
> Sprint & Network Virginia. Even the Sprint looking glass shows no sign 
> of a Sprint path to us.
>    The one exception is which shows about 
> 50... almost all of which are C&W.
>    If I pull down the C&W circuit, things shift and Sprint starts 
> showing up with multiple paths in all the looking glasses but will 
> remain that way after the C&W circuit comes back online until I bring 
> down the Sprint circuit. It seems to be one or the other... but never both.
>    Is this not a big deal and I'm misreading the situation, or has 
> something changed for the worse somewhere in our advertising and 
> relationship with our providers? I can't seem to track down a cause. 
> I've certainly made no changes to my BGP tables and announcements upstream.
>    For anyone interested in glancing at their routes for me, check 
> and AS 19138.
> Thanks!
>   - Aaron Mahler
> Sweet Briar College
> P.S. Feel free to yell at me if this post shouldn't be here. I've been 
> lurking for ages and enjoy following the discussions of the very 
> knowledgeable crew out there. Not sure what other forum to ask such a 
> question at this point...

Stephen J. Wilcox
IP Services Manager, Opal Telecom
Tel: 0161 222 2000
Fax: 0161 222 2008