Getting ipv6 to work with a Kimsufi server

Starting from yesterday, my server (phyks.me) should be available using ipv6. This was not the case before due to laziness and a lack of configuration. However, as setting ipv6 on a Kimsufi seems to not be really straight-forward (out of date documentation, information disseminated over the web and difficult to find between basic mistakes and real errors…), I think it may be useful to keep some notes here. Hope it can help anyone.

The doc explains that OVH has not set ipv6 autoconfig on their servers, and that you should configure the default route and IP address yourself.

To find your ip address, it is pretty easy: just go to your manager and look for the ipv6 address in the IP section.

$ ip -6 addr add YOUR_IPV6_ADDRESS/64 dev eth0

This will add the ipv6 address to your network device. Then, you have to manually add the default gateway. To get its address, you should remove the last two digits of your ipv6 address and put FF:FF:FF:FF:FF instead. This means that 2001:41d0:1:4462::1/64 will give you a default gateway 2001:41d0:1:44FF:FF:FF:FF:FF.

Then, you should add a default route via this gateway

$ ip -6 r a default via 2001:41d0:1:44FF:FF:FF:FF:FF

This is the standard procedure explained in OVH guide and many posts around the web such as this one (in French). It may work in some cases, however, in my case, I could not reach the default gateway and then, I could not add this route.

I found a comment on the OVH forum giving a solution.

You should first add a route to reach the gateway

$ ip -6 r a 2001:41d0:1:44FF:FF:FF:FF:FF dev eth0

and then, you can add the default route via this gateway

$ ip -6 r a default via 2001:41d0:1:44FF:FF:FF:FF:FF