IPv6 in broken state

Question

IPv6 has been unuseable latetly. Its not just about the unsupported PD-IA over PPPoE which has not been fixed since i reported it 1 1/2 years ago (several times and in beta), but with the last few updates IPv6 seems to only work in midnight during full moon if you spell the right chants. Sometimes it works, sometimes i need to restart the UTM a few times turn off/on IPv6. 
 Is anyone else having these problems? 
 If Sophos is reading this: when are you going to fix remaining buggy implementation?

PrakashSwamy · Answer

We recently identified the root cause for a similar issue related to IPv6. The issue was with low-speed (<=1 Gig) eth interfaces and the solution for it was to disable GRO (generic-receive-offload) for the eth interfaces on the UTM. 
 
 You may try the following configuration for the eth interfaces on your device and see if it helps solve the issue you are facing: 
 1. Disable GRO using "ethtool --offload eth<x> gro off" 
 2. If step '1' doesn&rsquo;t solve the issue, also try disabling other offloading features like GSO, TSO, LRO, etc 
 
 If this solution doesn't work, please provide more information about the NICs (like device-id, vendor-id, etc), interface speed and the kernel/ network driver version on your device. 
 
 Thanks, 
 Prakash

Ben · Answer

UPDATE: Sophos created a private patch for our UTM that fixes/enabled ipv6 prefix delegation over pppoe! I am testing this patch right now and i suspect (but can't say for sure) that they will include it in one of their next patches (at least that would make sense, sophos has not said that they will do that, so its me speculating that they will) 
 i will post the BUG ID here so that anyone affected by this bug can ask their sophos partner to request this bugfix and have it installed (IF thats how "it" works) 
 Edit/Update: The fix works and the BUG ID is "NUTM-7187" 
 Edit2: Hold your breath, delegated ipv6 prefix doesn't work after 24-48 hours, i will try to file a new bug report tomorrow. It seems the utm doesn't renew the prefix after the lease time runs out. Probably a slight oversight...

Soong · Answer

So I did bail on Sophos but I haven't forgotten those still suffering. I came across a bug in the Router Advertisement daemon on another router; it wouldn't start if more than two IPv6 DNS servers were specified. I'm sure I had at least 4 configured on my UTM. Anyway, try removing all IPv6 (or all but two) DNS servers from your UTM configuration (maybe reboot or turn off and on the IPv6 functionality to ensure the services are [re]started). 
 BTW My APs for sale , red 50