I'm very glad this email thread has occurred... I was hoping to deploy two 
pfSense boxes as IPv6 routers.
Now I'm wondering if I should just put in OpenBSD at least for now?
-Adam

Adam Hunt <[email protected]> wrote:

>Thanks for the explanation Chris. I did run across a bug report that seems to 
>be exactly what we're running into (http://redmine.pfsense.org/issues/2129).
>
>
>Are the issues with v6 fragmentation inherent to FreeBSD 8.3 that pfSesne 2.1 
>is based on? Also, are there any workarounds for those of us running 2.1? I'm 
>not sure when 2.2 will be tagged but it would great if there was some way, 
>maybe by adjusting the MTU and/or MSS values, that those of us affected by 
>this bug could use get their v6 tunnels up and running, even if not at their 
>theoretical peak efficiency.
>
>
>Thanks for all the help. I realize IPv6 support can be more than a little 
>tricky. I really appreciate all the work that everyone has done on pfSense, 
>it's a great tool.
>
>
>--adam
>
>
>
>On Thu, Aug 15, 2013 at 6:20 PM, Chris Buechler <[email protected]> wrote:
>
>On Thu, Aug 15, 2013 at 3:23 PM, Adam Thompson <[email protected]> wrote:
>>
>> Even weirder…
>>
>> Although I can successfully ping at payload sizes up to 1432, I see another 
>> more troubling problem:  there’s a “hole” where it works
>> with payloads up to 1232, fails with payloads between 1233 and 1255 
>> inclusive, then works again with payloads 1256 bytes and above. > WTF????
>>
>
>The original scenario, the diff between 1232 and 1233 is that at 1233,
>the echo request no longer fits in the minimum IPv6 size, so it's
>fragmented.
>20:16:33.241123 IP6 2610:160:11:33::230 > 2610:160:11:3::100: frag
>(0|1232) ICMP6, echo request, seq 2, length 1232
>20:16:33.241129 IP6 2610:160:11:33::230 > 2610:160:11:3::100: frag (1232|176)
>
>no response to the fragmented request.
>
>20:16:37.260945 IP6 2610:160:11:33::230 > 2610:160:11:3::100: ICMP6,
>echo request, seq 0, length 1408
>20:16:37.262526 IP6 2610:160:11:3::100 > 2610:160:11:33::230: ICMP6,
>echo reply, seq 0, length 1408
>
>bigger request that isn't fragmented is fine.
>
>If you don't specify -m on ping6 (at least with the FreeBSD ping6,
>others are likely similar), ping6 asks the kernel to fragment packets
>to fit the minimum IPv6 MTU, 1280.
>
>PF has issues with v6 fragmentation that we won't be able to address
>until 2.2, which is the root of the problem.
>
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