Cogent & Level 3 routing issue?

Matthew Crocker matthew at
Sat Dec 7 20:14:17 UTC 2013

Anyone seeing issues between Cogent & Level3 in NYC?

I have Sprint & Cogent for bandwidth.   Everything has been humming along for a couple years just fine.   Yesterday around 8:00AM my BGP session with Cogent flapped.  Now, when my Cogent BGP is up I get 100% packet loss in level3 land.  When Cogent BGP is down (i.e. I’m running solely on Sprint)  Everything is fine.

I have an open ticket with Cogent.  They say they have a ‘capacity issue’ with level3 that has been escalated to executive levels.

With Sprint & Cogent BGP UP
 I see traceroutes showing traffic leaving me on Sprint but returning on Cogent (and failing at level3).  I’m guessing it is the level3/cogent border

With Sprint UP & Cogent Down
 I see trace routes showing traffic on to/from on Sprint just fine.

Anyone else having issues?


Matthew S. Crocker
Crocker Communications, Inc.
PO BOX 710
Greenfield, MA 01302-0710

E: matthew at
P: (413) 746-2760
F: (413) 746-3704

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