Cogent input

Paul Stewart pstewart at
Thu Jun 11 13:55:06 UTC 2009

Our experience with them was at least one major (longer than an hour)
outages PER MONTH and many of those times they were black holing our
routes in their network which was the most damaging aspect.  The outages
were one thing but when our routes still somehow managed to get
advertised in their network (even though our BGP session was down) that
really created issues.  I have heard from some nearby folks who still
have service that it's gotten better, but we are also in the "regional
offering" when it comes to IP Transit and have sold connections to many
former Cogent customers who were fed up and left.

I have found with Cogent that you will get a LOT of varying opinions on
them - there are several other players (at least in our market) that are
priced very similar now and have a better history behind them.....

The specific de-peering issues never effected us much due to enough
diversity in our upstreams and a fair amount of direct/public peering...



-----Original Message-----
From: Justin Shore [mailto:justin at] 
Sent: Thursday, June 11, 2009 9:47 AM
Subject: Cogent input

I'm in search of some information about Cogent, it's past, present and 
future.  I've heard bits and pieces about Cogent's past over the years 
but by no means have I actively been keeping up.

I'm aware of some (regular?) depeering issues.  The NANOG archives have 
given me some additional insight into that (recurring?) problem.  The 
reasoning behind the depeering events is a bit fuzzy though.  I would be

interested in people's opinion on whether or not they should be consider

for upstream service based on this particular issue.  Are there any 
reasonable mitigation measures available to Cogent downstreams if 
(when?) Cogent were to be depeered again?  My understanding is that at 
least on previous depeering occasion, the depeering partner simply 
null-routed all prefixes being received via Cogent, creating a blackhole

essentially.  I also recall reading that this meant that prefixes being 
advertised and received by the depeering partner from other peers would 
still end up in the blackhole.  The only solution I would see to this 
problem would be to shut down the BGP session with Cogent and rely on a 
2nd upstream.  Are there any other possible steps for mitigation in a 
depeering event?

I also know that their bandwidth is extremely cheap.  This of course 
creates an issue for technical folks when trying to justify other 
upstream options that cost significantly more but also don't have a 
damaging history of getting depeered.

Does Cogent still have an issue with depeering?  Are there any 
reasonable mitigation measures or should a downstream customer do any 
thing in particular to ready themselves for a depeering event?  Does 
their low cost outweigh the risks?  What are the specific risks?




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