IPv6 MTU discrovery -- how should it work?

[Seth Mos]

Make sure you do not block icmp6. Or atleast make sure that unreachable and toobig packets come through even if you do not want echo.

Cheers,
Seth

typed on a tiny touchscreen, why exactly?

Lev Serebryakov <lev at FreeBSD.org>schreef:

>Hello, Freebsd-net.
>
> My  home network is connected to IPv6 world with Hurricane Electric's
>tunnel (IPv6 over IPv6, "gif").
> It has MTU 1280.
>
> Everything  works till packets are small -- for example, interactive
>shell (ssh) session over IPv6 works great. But when I need to transfer
>buil  of  bytes  from  server  to  local  network  (scp,  or even fast
>scrolling of man page in interactive session) traffic hangs. It starts
>to work after couple (5-10) minutes, but many applications has timeouts
>less, that that, and it is very annoying in any case.
>
>  When I connect to external server twice, and run tcpdump in one
>session for another one, and then try to use second (sniffed) session
>for bulk transfer, I can clearly see, that server tries to send IPv6
>packets with size 1420 to my local  network  many  times  and  doesn't
>get any answer, so it is MTU problem for sure, but how it could be fixed?
>
> Also, Youtube doesn't work over IPv6 with same symptoms, so it is not
>only  my servers' problem, it looks like my local network (and tunnel)
>problem.
>
> How should it work? Maybe, I'm filtering out something mandatory on firewall?
>
>-- 
>// Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>
>
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