It occurred to me that Ignatios Souvatzis wrote in
gmane.os.netbsd.devel.network:

> Yes, but what outer address did you use for your view of your end of the
> tunnel? The poster uses a public address - I can't quite see how this is
> supposed to work, and he doesn't explain.

I did, a few weeks ago ;), but a quick recap:

My modem doesn't offer bridging, but it does offer a DMZ of some sorts. 
My public IP is 85.145.84.197, and that's the official endpoint of the
tunnel. (The other end being at 131.155.141.2). The private IP of my modem
is 192.168.5.1. It *should* NAT all traffic to 192.168.5.2, but for some
strange reason it fails to do so for IP protocols it doesn't know about
itself (Including proto 41, aka gif). That traffic is still bridged to
the inside network, and it's being transmitted with the ethernet address
of 192.168.5.2 as target address, but the IP header isn't rewritten properly;
it still reads "85.145.84.197" as destination. So in fact, it's doing a 
bridge instead of a NAT, but only for proto 41. I initially added the
appropriate alias to rtk0, my interface connected with the modem, but that
didn't quite work out. Moving the alias to lo0 did. 

I tried putting back the alias to rtk0, but that didn't help. And I'm not
convinced my slightly dodgy network setup is to blame - I see traffic coming
in and out of my tunnel - just neighbourhood discovery seems broken.

-- 
    Martijn van Buul - pino@dohd.org - http://www.stack.nl/~martijnb/
	 Geek code: G--  - Visit OuterSpace: mud.stack.nl 3333
 The most exciting phrase to hear in science, the one that heralds new
discoveries, is not 'Eureka!' (I found it!) but 'That's funny ...' Isaac Asimov