I got IPv6 working with my home router, DD-WRT, and Comcast’s 6to4 service.
[6to4](http://en.wikipedia.org/wiki/6to4) works by setting up a tunnel for IPv6 over IPv4. It uses the anycast address 192.88.99.1 as the tunnel endpoint. The IPv6 address is constructed from the host’s IPv4 address with 2002: prefix. 6to4 only works for hosts with public IP address which is why it has to be run on the router. [Comcast has 6to4 proxies](http://www.comcast6.net/6to4-config.php). [Comcast was testing 6RD](http://www.comcast6.net/6rd-config.php) which is similar but the prefix and proxy address are configured.
First, I had to flash [DD-WRT to my WRT400N](http://www.dd-wrt.com/wiki/index.php/Linksys_WRT400N). Second, I had to [enable IPv6](http://www.dd-wrt.com/wiki/index.php/IPv6). The [6to4 config for 2.6 kernels](http://www.dd-wrt.com/wiki/index.php/IPv6#6to4_on_k2.6_builds) requires a radvd config and startup script to be entered. Also, the scripts had to be changed for the WRT400N since they don’t have vlan2 device but eth1 worked.
radvd config:
interface br0 {
MinRtrAdvInterval 3;
MaxRtrAdvInterval 10;
AdvLinkMTU 1480;
AdvSendAdvert on;
prefix 0:0:0:1::/64 {
AdvOnLink on;
AdvAutonomous on;
AdvValidLifetime 86400;
AdvPreferredLifetime 86400;
Base6to4Interface eth1;
};
};
Startup script:
insmod /lib/modules/`uname -r`/kernel/net/ipv6/sit.ko
sleep 5
radvd -C /tmp/radvd.conf start
sleep 5
WANIP=$(ip -4 addr show dev eth1 | grep ‘inet ‘ | awk ‘{print $2}’ | cut -d/ -f1)
if [ -n “$WANIP” ]
then
V6PREFIX=$(printf ‘2002:%02x%02x:%02x%02x’ $(echo $WANIP | tr . ‘ ‘))
ip tunnel add tun6to4 mode sit ttl 255 remote any local $WANIP
ip link set tun6to4 mtu 1480
ip link set tun6to4 up
ip addr add $V6PREFIX:0::1/16 dev tun6to4
ip addr add $V6PREFIX:1::1/64 dev br0
ip -6 route add 2000::/3 via ::192.88.99.1 dev tun6to4
kill -HUP $(cat /var/run/radvd.pid)
fi
sleep 10
radvd -C /tmp/radvd.conf start