Frequently Asked Questions (FAQ)

How do I give connectivity to other hosts on my subnet?

The easiest way to use your subnet is to assign a /64 per network and then setup a Router Advertisement server. As SixXS serves out /48's, a so called site-prefix, as subnets you have the possiblity of having 65535 /64's and thus subnets inside your site. A /48 is an end-site and should thus not be delegated to other administrators.

Under Linux this Router Advertisement (RA) server is called radvd, *BSD (KAME stack) calls it rtadvd. Clients can then be configured using RFC 2462 aka "IPv6 Stateless Address Autoconfiguration".

Note well that in tunnels from the /64 only ::1 (the PoP) and ::2 (your endpoint) can be used as the rest is not routed. Thus if you need to connect other hosts do it correctly and request a subnet.

Sharing your subnet to other sites is not allowed. If you want friends or other organisations to receive IPv6 connectivity, then help them setup their own account. Of course it is allowed to provide subnets to your own networks inside the same administrative site. In any way the person who owns the subnet is responsible, if anything that violates this FAQ happens, that account is disabled.

A site is defined as a network with one single administration. The moment a change occurs in administration, one is in a different site. Thus if you have 1 building operated by administration group X and another building operated by admin Y then those are two sites. Of course, when group X and Y, both administratively fall under group A, they can still be taken as to be a single site where wanted.

Linux - Router

Get yourself the radvd program. On Debian you can install the radvd program by doing an 'apt-get install radvd' other distributions have a similar name for the package.

Edit /etc/radvd.conf to contain something like:
interface eth1
{
  AdvSendAdvert on;
  prefix [IPv6 Prefix]/64
  {
  };
};

The full format is described in the manual pages of radvd. Note that a link has a prefixlength of /64.

You will also need to add a single IP out of the above block to the interface itself, this as the machine won't accept the RA from itself due to when forwarding is enabled, RA gets disabled.

Now start the radvd program and your machine should starting announces its routes.
Notez bien that this needs needs the net/ipv6/conf/all/forwarding sysctl to be 1 and that, depending on radvd version, you might have to add an IPv6 address out of the to-be-RA'd prefix on the interface before starting radvd.

Another thing you might want to do, to avoid traffic being routed back to the tunnel when you are not using all of your /48 is to point the /48 in its entirety to lo:
ip -6 ro add [IPv6 Prefix]/48 dev lo
On debian one can accomplish this from the network scripts.

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