IPv4 over IPv6

Another LAB:

Note that R4 is not relevant for this post and will be used later on.

R2, R3 and R5 are all configured with IPv6 address and running EIGRP AS100,

the basic IPv6 EIGRP configuration on each router is basiclly the same beside the IPv6 addresses:

R2:

ipv6 unicast-routing

!

int s2/0

ipv6 address 2001:23::2/112

ipv6 eigrp 100

!

ipv6 router eigrp 100

eigrp router-id 2.2.2.2

no shutdown

!

pay attention not to forget the no shutdown under the IPv6 EIGRP process else the EIGRP process will not run and % EIGRP 100 is in SHUTDOWN message will be shown while trying to see neighbors.

R2 and R1 are directly connected with IPv4 and running OSPF(v2), R2 is advertising default-route originate always to R1 and pretty much the same for R5 and R6.

Now my goal is to connect R1 and R6 to share the same routing information using OSPF as routing protocol.

i have configured an IPv6 tunnel from R2 to R5, as IPv6 source and destination and used IPv4 as inner IP addresses for the tunnel.

R2:

interface Tunnel0
 ip address 192.168.1.2 255.255.255.252
 tunnel source 2001:23::2
 tunnel destination 2001:35::5
 tunnel mode gre ipv6

R5:

interface Tunnel0
 ip address 192.168.1.1 255.255.255.252
 tunnel source 2001:35::5
 tunnel destination 2001:23::2
 tunnel mode gre ipv6

this tunnel allowed me to run OSPF between R1 and R6:

R1#sh ip route ospf
     10.0.0.0/24 is subnetted, 2 subnets
O       10.1.45.0 [110/1002] via 10.1.12.2, 00:09:38, FastEthernet0/0
     192.168.1.0/30 is subnetted, 1 subnets
O       192.168.1.0 [110/1001] via 10.1.12.2, 00:09:38, FastEthernet0/0
O*E2 0.0.0.0/0 [110/1] via 10.1.12.2, 00:09:38, FastEthernet0/0