Seeking Comcast Contact: need to troubleshoot packet loss and/or asymmetric routing issue between Comcast & Onvoy
Robert Boyle
robert at tellurian.com
Thu Aug 2 15:49:44 UTC 2007
At 09:30 AM 8/2/2007, Craig D. Rice wrote:
>For four months dozens of our users who are Comcast subscribers have
>had difficulty reaching St. Olaf College's and Carleton College's
>network services.
>
>We have worked through everything we can think of with our Onvoy
>(regional ISP) network engineers. We have isolated the problem a
>couple of Comcast's IP subnets, but need a contact within Comcast to
>further troubleshoot.
(snip)
Either your firewall/router or the customer's firewall/router is
blocking PMTUD packets. Fragment needed, but don't fragment bit set.
Look at your ICMP access list and make sure you are allowing: permit
icmp any any unreachable from any Internet address. I suspect an
overzealous firewall admin is blocking all icmp. Read the acronym to
him/her and explain that some icmp is necesary for the Internet to work.
-Robert
Tellurian Networks - Global Hosting Solutions Since 1995
http://www.tellurian.com | 888-TELLURIAN | 973-300-9211
"Well done is better than well said." - Benjamin Franklin
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