Cogent latency / congestion

Steve Gibbard scg at
Mon Aug 20 21:43:45 UTC 2007

On Mon, 20 Aug 2007, Mike Tancsa wrote:

> Bell uses Cogent in a large way. The second traceroute was from an IP in 
> their AS (577) out.   I am prepending out Cogent, but Bell does everything it 
> can not to use Teleglobe so I am having problems influencing their routes to 
> come back that way.  They also have a very odd path out of Chicago.  This is

Bear in mind that doing "everything they can not to use Teleglobe" 
probably involves local preference.  Local preference comes before AS path 
length in the BGP selection order, so nothing you can do with prepending 
is going to help.  You'll need to either keep them from seeing the 
undesirable path at all (drop the announcement, ask your upstreams to 
limit its propagation, etc.) or convince Bell not to use it.  Depending on 
the setup, you may be able to limit route propagation with communities, or 
it may require some phone calls.


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