[ipv6-wg] IPv6 cloud!

On 09/05/16 22:09, Benedikt Stockebrand wrote:
>>> Considering the increasing reports of people having problems with
>>> DS-Lite 
>>
>> Any more details on that?
>>
> And apparently various VPN solutions, too, but I never got access to
> any details with this.

I came across this recently (my ISP now provides native IPv6 + DS-lite
IPv4), and after debugging it, found that the CPE device was reporting
an incorrect path MTU when receiving a DF packet that was larger than
the tunnel interface to the AFTR.

This caused UDP IPv4 OpenVPN tunnels to stall and die horribly. I worked
around it by overriding the link-mtu config in OpenVPN.

But in this case, it was the CPE, not the AFTR, causing the problem.

(Of course I sent the ISP tcpdumps and a full analysis pointing out to
them that the firmware in the CPE they provided me was broken. They
decided to fix it by sending me a different model of CPE. I doubt they
ever escalated it to actually fix the underlying problem in the original
CPE. But if you happen to have a Technicolor TC7200, be wary of its
DS-Lite implementation!)

Cheers,
Colin