IPv6 on Comcast

I recently switched back to Comcast, and given that they have been talking up their IPv6 initiatives a lot, I decided to see how easy it was to get IPv6 connectivity. As it turns out, it was almost trivial.

While Comcast is planning to have dual-stack (both IPv6 and IPv4) support soon, they currently only support 6to4 in my area. The good news is that they support automatic 6to4 tunnel configuration.

Here is how I got it working with my Mac.

1. I unplugged my router and connected my Mac directly to the cable modem (6to4 tunneling does not work behind a NAT gateway -- well sort of, but I'll save that for a future blog when I get it working).
2. I restarted the cable modem (if you don't do this, it will stay bound to your router's MAC address and you won't get any connectivity).
3. I waited for things to settle down (the cable modem has a bad habit of giving you a 192.168.100.x address space temporarily, but unplugging the ethernet cable from your computer and/or renewing your DHCP on your computer should fix it).
4. You should now have regular IPv4 connectivity.
5. Now the cool part. In the System Preferences network settings, I clicked the "+" to add a new network, and chose "6 to 4" for the interface type.
6. I then opened a browser to ipv6.google.com and voila, it worked.

Of course, this was a temporary solution because I had to unplug my router. However, I've heard that several people have had success with the Apple Airport Extreme and several of the other routers listed on the 6to4 Wikipedia page.

I plan to do some more experiments with DD-WRT or Linux as the router. Stay tuned.