Seeking UUNET/Level3 help re packet loss between Comcast & Onvoy customers

Rich Graves rgraves at carleton.edu
Wed Aug 29 19:24:56 UTC 2007


This is resolved, though no one knows exactly why. If someone at Global Crossing has relevant logs of route flaps or somesuch, that might be interesting, but I can live with the mystery.

Comcast advertises a specific route for the "problem" space, 71.63.128.0/17. Don't ask me why. Early yesterday morning, they flapped that route -- stopped advertising it, then started again. *Probably* shortly after that, and possibly as a consequence, our connectivity to the range of Comcast IP addresses typically assigned to residential customers in MN was restored.

Our ISP, Onvoy, has three upstreams: Verizon, Global Crossing, and AT&T.

The route from 137.22/16 and 130.71/16 to Comcast typically took the path

carleton->onvoy->global crossing->level3->at&t->comcast

But the path from Comcast to us was simply

comcast->at&t->onvoy->carleton

For some time, Global Crossing was a mystery hop, because Onvoy was not terribly communicative, and Global Crossing was not showing up in traceroutes. Onvoy has let us know that this was could have been because the glbx/onvoy link was filtering ICMP due to DDoS attacks, but this seems wrong to me on a number of levels. Anyway, it's "fixed."
-- 
Rich Graves http://claimid.com/rcgraves
Carleton.edu Sr UNIX and Security Admin
CMC135: 507-646-7079 Cell: 952-292-6529



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