Concerning the hardware, we have two cisco 3825 connnected via a WAN. Just call them router_1 and router_2. We use two laptops to configure it via telnet, using putty. Concerning the IOS, it is a 12.4(24)T.
We have configured in each cisco, two VRF named EXP and EXP3 using "vrf definition EXP" instead of "ip vrf EXP". VRF EXP stands for IPv4 experiments and VRF EXP3 stands for IPv4/IPv6 experiments.
Then we have built only one tunnel GRE between both routers more exactly between the VRF EXP of each routers.
We have put BGP protocol on each router to exchange ip information between VRF EXP and VRF EXP3.
We have set up OSPF protocol between the two routers to exchange dynamically routes into each VRF EXP.
The IPv4 communication works fine between the VRF EXP3 via the tunnel GRE which link the two VRF EXP.
We would like to do the same thing in IPv6 but we can not set up Ipv6 ospf protocol into VRF EXP.