Comcast6.net PMTU broken

[Ryan Rawdon]

On Apr 17, 2012, at 5:24 PM, Ryan Rawdon wrote:

> From a host behind a 6in4 tunnel a request to www.comcast6.net hangs.  It looks like a PMTU brokenness issue since the connection is established and the request is sent successfully.


I've gotta follow-up to my original message and say I'm not quite sure what is going on.  Doing more testing I am sporadically having the symptom shown below mixed in with attempts which outright fail to connect (coupled with at least one person on IRC who isn't able to connect to the same address).  I am so far unable to reproduce it from other sites with a 1280 MTU

Foot in mouth - looks like it is not necessarily a PMTU issue.

> 
> Requesting the same page from a host with a 1500B path MTU succeeds.
> 
> nova-dhcp-host111:tmp ryan$ wget http://www.comcast6.net
> --2012-04-17 17:17:16--  http://www.comcast6.net/
> Resolving www.comcast6.net (www.comcast6.net)... 2001:558:1002:4:68:87:29:36, 68.87.29.36
> Connecting to www.comcast6.net (www.comcast6.net)|2001:558:1002:4:68:87:29:36|:80... connected.
> HTTP request sent, awaiting response... ^C
> 
> 
> This only happens with 2001:558:1002:4:68:87:29:36.  2001:558:1004:9:69:242:76:78 (which I've seen listed for www.comcast6.net though I do not see it in DNS currently) does not have this problem