Cisco IOS Cookbook, 2nd Edition

Tunneling IPv6 Through an Existing IPv4 Network

Problem

You want to connect two IPv6 networks through an existing IPv4 network that doesn’t natively support IPv6.

Solution

The easiest way to pass IPv6 traffic through a section of IPv4 network that doesn’t offer native IPv6 support is to create a simple GRE tunnel:

Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#interface Loopback1
Router1(config-if)#ip address 10.15.1.11 255.255.255.255
Router1(config-if)#exit
Router1(config)#interface Tunnel1
Router1(config-if)#ipv6 address BBBB:1::1/126
Router1(config-if)#ipv6 rip RIP_PROC enable
Router1(config-if)#tunnel source 10.15.1.11
Router1(config-if)#tunnel destination 172.16.11.9
Router1(config-if)#exit
Router1(config)#end
Router1#

And then you configure the device on the other end similarly:

Router9#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router9(config)#interface Loopback1
Router9(config-if)#ip address 172.16.11.9 255.255.255.255
Router9(config-if)#exit
Router9(config)#interface Tunnel1
Router9(config-if)#ipv6 address BBBB:1::2/126
Router9(config-if)#ipv6 rip RIP_PROC enable
Router9(config-if)#tunnel source 172.16.11.9
Router9(config-if)#tunnel destination 10.15.1.11
Router9(config-if)#exit
Router9(config)#end
Router9#

Discussion

This example is actually simpler than a lot of GRE tunnel configuration examples because the protocol used to support the tunnel end points is different from the protocol ...