6to4 Tunneling

6to4 Tunneling
6to4 tunneling is really useful for carrying IPv6 data over a network that’s still IPv4. It’s quite
possible that you’ll have IPv6 subnets or other portions of your network that are all IPv6, and
those networks will have to communicate with each other. That’s not so complicated, but
when you consider that you might find this happening over a WAN or some other network
that you don’t control, well, that could be a bit ugly. So what do you do about this if you don’t
control the whole tamale? Create a tunnel that will carry the IPv6 traffic for you across the
IPv4 network, that’s what.
The whole idea of tunneling isn’t a difficult concept, and creating tunnels really isn’t as
hard as you might think. All it really comes down to is snatching the IPv6 packet that’s happily
traveling across the network and sticking an IPv4 header onto the front of it. It’s kind of like
catch-and-release fishing, except the fish doesn’t get something plastered on its face before
being thrown back into the stream.
To get a picture of this, take a look at Figure 10.2.