Almost There
Now that we have an active tunnel, it's time to set up the local eth0 interface to use it. There are only two steps:
Step One: Tell The Kernel About IPv6 and Routing
Just like IPv4, unless the kernel knows IPv6 is there, it's not going to work. And, just because it's there doesn't mean it will be routed between interfaces. To fix both of these things requires editing a few files:
1. Edit /etc/sysctl.conf
Add the line
net.ipv6.conf.all.forwarding = 1
This will inform the kernel that forwarding is allowed on all IPv6 interfaces.
2. Edit /etc/sysconfig/network
Add a line that says
NETWORKING_IPV6=Yes
This makes sure IPv6 is available at boot.
3. Edit /etc/sysconfig/network-scripts/ifcfg-eth0
You will see the usual lines set up for this interface in IPv4 mode. Add the following lines:
IPV6INIT=Yes
IPV6ADDRESS=2001:470:d:60c:0001::1/64;
What do these lines do?
The first line tells the networking subsystem that this interface can handle IPv6. Without it, you don't get it. The second assigns an address to it. Think of this is a static IPv6 address. In this case, the interface will be assigned the (full) address:
20001:0470:000d:060c:0001:0000:0000:0001
Remember that, when absent, one can add a 0 and all addresses will be expanded to the full 128 bits.
4. Reboot
Upon reboot, we now have local IPv6 support.