OSPF Virtual Link 2

We know the virtual link for connect to OSPF backbone area 0.
How about two that network have 2 backbone area?

Figure 1.1

R1 and R6 can't connect.

R1(config-router)#do sh ip route ospf
     3.0.0.0/24 is subnetted, 1 subnets
O IA    3.3.3.0 [110/3] via 10.1.12.2, 00:22:38, FastEthernet0/0
     4.0.0.0/24 is subnetted, 1 subnets
O IA    4.4.4.0 [110/4] via 10.1.12.2, 00:21:52, FastEthernet0/0
     10.0.0.0/24 is subnetted, 3 subnets
O IA    10.1.23.0 [110/2] via 10.1.12.2, 00:23:28, FastEthernet0/0
O IA    10.1.34.0 [110/3] via 10.1.12.2, 00:22:38, FastEthernet0/0

R6(config-if)#do sh ip route ospf
     3.0.0.0/24 is subnetted, 1 subnets
O IA    3.3.3.0 [110/4] via 10.1.56.5, 00:16:06, FastEthernet0/0
     4.0.0.0/24 is subnetted, 1 subnets
O IA    4.4.4.0 [110/3] via 10.1.56.5, 00:16:06, FastEthernet0/0
     10.0.0.0/24 is subnetted, 3 subnets
O IA    10.1.45.0 [110/2] via 10.1.56.5, 00:16:06, FastEthernet0/0
O IA    10.1.34.0 [110/3] via 10.1.56.5, 00:16:06, FastEthernet0/0

Not only Router 3 can connect to Router 1 but also Router 4 can connect to Router 6.

R3#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/57/64 ms
R3#ping 6.6.6.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

R4#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R4#ping 6.6.6.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 48/83/140 ms

In this cause, we can solve with Virtual Link

Only configure Virtual Link at area 51.

R3
router ospf 1
area 51 virtual-link 4.4.4.4

R4

router ospf 1
area 51 virtual-link 3.3.3.3

Just do like my old post.

http://outbox-network.blogspot.com/2016/03/ospf-virtual-link-ospf-virtual-link-is.html.

After Configure virtual link you will see result like that.

R1#sh ip route ospf
6.0.0.0/24 is subnetted, 1 subnets
O IA 6.6.6.0 [110/6] via 10.1.12.2, 00:00:00, FastEthernet0/0

R6
R6#sh ip route ospf
1.0.0.0/24 is subnetted, 1 subnets
O IA 1.1.1.0 [110/6] via 10.1.56.5, 00:01:41, FastEthernet0/0

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