[Nanog] Cogent Router dropping packets

David Coulson david at davidcoulson.net
Mon Apr 21 16:02:49 UTC 2008

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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