[174821] in North American Network Operators' Group
Re: cogent update suppression, and routing loops
daemon@ATHENA.MIT.EDU (Jon Lewis)
Thu Oct 2 18:19:51 2014
X-Original-To: nanog@nanog.org
Date: Thu, 2 Oct 2014 18:19:41 -0400 (EDT)
From: Jon Lewis <jlewis@lewis.org>
To: ryanL <ryan.landry@gmail.com>
In-Reply-To: <CAK_-TSZuQ5Sng5J1rot_=pDLfajGUyNJVDRjzJo9AzaMPhxH4w@mail.gmail.com>
Cc: North American Network Operators Group <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Thu, 2 Oct 2014, ryanL wrote:
> hi. relatively new cogent customer. is what i've stated in my subject line
> kinda standard fare with them?
>
> i've discovered that when i advertise a /24 from inside a larger /22 to XO,
> (who peers with cogent), and then pull the /24 some time later, that cogent
> holds onto the /24 and then bounces packets around in their network a bunch
> of times for upwards of 8-10 minutes until they finally yank it. this
> effectively blackholes traffic to my /24 for anyone that is using a path
> thru cogent.
Perhaps related, I made an as-path prepend change on a route advertised to
Cogent yesterday and noticed it took about 10 minutes for that change to
propagate throughout Cogent's network and be visible on route-views. A
moment later, I did the same thing with another carrier, and got the
expected nearly instant gratification. Perhaps they've got a bunch of
routers configured with minimum-advertisement-interval to batch the BGP
updates and if you're unlucky with the timing, it can take a while for
routes/changes to percolate through their network? Imagine driving down a
long road, where every traffic light turns red just before you get to the
intersection. Wait a minute here, wait a minute there...
----------------------------------------------------------------------
Jon Lewis, MCP :) | I route
| therefore you are
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