Seeking Comcast Contact: need to troubleshoot packet loss and/or asymmetric routing issue between Comcast & Onvoy

William Herrin herrin-nanog at
Thu Aug 2 14:09:38 UTC 2007

On 8/2/07, Craig D. Rice <cdr at> wrote:
> We have already attempted the usual troubleshooting and have eliminated user
> problems, computer problems, server problems, cable modem problems, and
> Linksys router problems. Traceroutes have been somewhat inconclusive since
> Onvoy blocks ICMP within its network.


This rings a bell. Do they block the mandatory ICMP
fragmentation-needed messages?

Try this: on your web server, reduce the MTU from 1500 bytes to 1400
bytes and see if the affected comcast users can now access your web

Bill Herrin

William D. Herrin                  herrin at  bill at
3005 Crane Dr.                        Web: <>
Falls Church, VA 22042-3004

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