nanog mailing list archives

Re: [Nanog] Cogent Router dropping packets


From: David Coulson <david () davidcoulson net>
Date: Mon, 21 Apr 2008 12:02:49 -0400

Joe Greco wrote:
For those unfamiliar, Cogent has a system where you set up an EBGP peering
with the Cogent router you're connected to, for the purposes of announcing
your routes into Cogent.  However, these are typically smaller, aggregation
class routers, and do not handle full tables - so you don't get your routes
from that router.  To get a full table FROM Cogent, you need to set up an
EBGP multihop session with them, to their nearest full-table router.  I 
believe they actually do all their BGP connections in that manner.
Depends on the service you purchase. Fast Ethernet seems to be delivered 
as eBGP-multihop (the first hop is just a L3 switch), however DS-3 is 
handled as a single BGP session. I'm not sure if GigE or SONET services 
are handled as multihop or not.

Probably all depends what hardware they have at each POP....



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