IPv6to4

My friend and colleague Lapo Luchini saw my post about how I got a couple of SixXS tunnels. It turns out, he used to be their user, too, but had to quit when they got less than friendly after a couple of their mails bounced back. He was very kind to explain how he set up 6to4 on his box. Indeed, it's dead simple.

ipv6_enable="YES"
stf_interface_ipv4addr="193.234.15.7"
ipv6_defaultrouter="2002:972d:1502::"

That's all I had to add to rc.conf(5). I than ran

/etc/rc.d/network_ipv6 start
route add -inet6 default 2002:972d:1502::

and everything just worked. 6to4 is described in RFC 3056. stf_interface_ipv4addr is the IPv4 address you'll be using for the tunnel endpoint. ipv6_defaultrouter is the address of your 6to4 relay. Usually 2002:c058:6301:: is the universal address of free 6to4 relays. If an ISP wants to set up one of his own, he assigns this well-known address to it (which is 192.88.99.1 in IPv4 notation) and advertises a route to 192.88.99/24. Unfortunately, our ISP (http://www.free.net/) apparently messes up the route (probably making it a black hole). Instead, they provide another IP address to be used as a 6to4 relay. Fortunately, it works.

At home I've got ADSL with a dynamic IPv4 address. I could use 6to4, but my IPv6 addresses would be dynamic, too. Currently I use a SixXS tunnel, which provides a static IPv6 address. Whenever my ADSL gets shaky and does its lose-sync-retrain-reconnect thing, the IPv4 address changes, but my TCPv6 sessions get a fair chance to continue working like nothing ever happened. On the downside, the remote tunnel endpoint is over 80 ms of RTT away, which is a considerable component of latency. So all I have to hope for is either a new SixXS endpoint in Russia or native IPv6 connectivity from my ADSL provider. Or, if I get too desperate, I may route a portion of the 6to4 blocks from work to home.