Hi all, I thought I'd post this, since it took us some time to figure out and I can imagine other people having the same difficulty. The setup is as follows: Linux device behind a Thomson Speedtouch ADSL modem is the one initiating the IPv6 tunnel to SixXS. This is my first post about it and this the second, with the final solution. If you don't need instructions on how to connect to your modem, you only need the second one. Hope this helps someone!