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 From:  Jakob Schwienbacher <jakob dot schwienbacher at gmail dot com>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Re: setting up an IPv6 tunnel
 Date:  Sat, 19 Mar 2011 12:25:28 +0100
Hello Brian,

Fine to hear that your tunnel is working now properly. Since the IPv6
MTU is handled in a different way than in IPv4, I didn't understand it
well right now.


I figured out a MTU size of 1280 (dirty ping & packet size). So I have
the MTU of 1280 on each IPv6 client. I have to do some tests in the
future to understand IPv6 MTU with tunnel configuration. Let me know
your configuration when it works properly.

Thank you,



On 18 March 2011 23:47, Brian Lloyd <brian dash wb6rqn at lloyd dot com> wrote:
> On Fri, Mar 18, 2011 at 7:34 AM, Brian Lloyd <brian dash wb6rqn at lloyd dot com> wrote:
>> One thing I just discovered is that I never added a firewall rule to pass
>> anything on the LAN side. (It has been a long time since I started m0n0wall
>> from scratch on a system.) I assumed (erroneously) that the firewall would
>> pass all traffic unless configured otherwise. I suspect that might have an
>> effect. ;-) I have now done so and will work on this again when I reach
>> school.
> Apparently I had everything properly set up. I had just forgotten to add a
> rule to permit IPv6 traffic through the firewall. It now passes most of the
> tests (I am getting variable results). It complains about large packets (I
> suspect MTU) and DNS. Since DNS passes some of the time I suspect that not
> all the name servers I use support IPv6.
>>> If the tunnel is established try to run test-ipv6.com. I had some
>>> troubles with MTU.
>> I would expect MTU issues on a tunnel. Either fragmentation needs to be
>> enabled or the IPv4 MTU needs to be large enough to allow for the IPv6
>> header overhead in the IPv4 tunnel payload.
> What did you end up setting your MTU to? The IPv6 header is 40 octets and
> the minimum MTU is 1280 so I would expect that a default IPv4 MTU of 1500
> should be sufficient. What did you find?
>> Now back to repairing the furnace in my house. (It seems that everything
>> breaks at once.)
> For those of you waiting in breathless anticipation of whether or not my
> house will have heat, I was able to repair my furnace. It turned out to be a
> bad solder joint on the control board where the fan relay plugs in.
> --
> Brian Lloyd, WB6RQN/J79BPL
> 3191 Western Dr.
> Cameron Park, CA 95682
> brian at lloyd dot com
> +1.767.617.1365 (Dominica)
> +1.931.492.6776 (USA)
> (+1.931.4.WB6RQN)