Setup isatap router on debian

The ifupdown package on Debian does not support isatap as a mode for v4tunnel. Therefore, one can not simply create a single entry in /etc/network/interfaces to make it work. Anyhow, following are the steps I took to set it up.

1. Install iproute and radvd
2. Add "net.ipv6.conf.all.forwarding=1" to /etc/sysctl.conf
3. Add /etc/radvd.conf containing:
   interface is0
   {
       AdvSendAdvert on;
       UnicastOnly on;
       AdvHomeAgentFlag off;
       prefix 2002:aaaa:bbbb:1::/64
       {
           AdvOnLink on;
           AdvAutonomous on;
           AdvRouterAddr off;
       };
   };
   (replace "2002:aaaa:bbbb:1" with the prefix of your ipv6 subnet)
4. Since I have my default address connected to a 6to4 tunnel on my eth0 already, I need to add an additional ip4 address to eth0. In /etc/network/interfaces I add the following post-up, and pre-down scripts to eth0:
   
   post-up ip tunnel add is0 mode isatap local 192.168.1.12 ttl 64
   post-up ip link set is0 up
   post-up ip addr add 2002:aaaa:bbbb:1::5efe:192.168.1.12/64 dev is0
   post-up ip addr add 192.168.1.12/32 dev eth0
   pre-down ip addr del 192.168.1.12/32 dev eth0
   pre-down ip link set is0 down
   pre-down ip tunnel del is0
   (again replace "2002:aaaa:bbbb:1")
5. Restart the computer or do the following:
   $ sysctl -p
   $ ifdown eth0
   $ ifup eth0
   $ invoke-rc.d radvd start
   

On the client side, I just installed isatapd, added

ISATAP_ROUTERS="192.168.1.12"

to /etc/default/isatapd, and restarted with "invoke-rc.d isatapd restart". Then, everything works!