Configuring Virtual Links on GNS 3

Please note that it is not recommended to design your network in a way that there is a network that will be not attached to Area 0 (The Backbone Network). If your caught up in this situation, by using the concept of Virtual Link we will allow the network which is not attached to Area 0 Directly to receive Routing Updates and being able to communicate with other networks on different Areas. 

Configuring a Virtual Link between R7 and R6 to enable R8 on Area 78 to receive OSPF Routing Updates.

Router ID for R7 is 7.7.7.7
Router ID for R6 is 6.6.6.6
Routing Protocol Configured: OSPF
Router 5 has redistribution configured due to 2 routing protocols working on the same router RIPv2 and OSPF

//Configuring Virtual Link between Router R7 and Router R6.

On R7
=================================================================
R7#config t
Enter configuration commands, one per line. End with CNTL/Z.
R7(config)#router ospf 1
R7(config-router)#area 67 virtual-link 6.6.6.6
R7(config-router)#end

On R6 

================================================================
R6#config t
R6(config)#router ospf 1
R6(config-router)#area 67 virtual-link 7.7.7.7
R6(config-router)#end

//Verifying the Status of the Virtual Links

On R6
=================================================================
R6#show ip ospf virtual-links

Virtual Link OSPF_VL0 to router 7.7.7.7 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 67, via interface Serial0/0, Cost of using 64
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:06
Adjacency State FULL (Hello suppressed)
Index 4/5, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec

On R7

==================================================================
R7#show ip ospf virtual-links

Virtual Link OSPF_VL0 to router 6.6.6.6 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 67, via interface Serial0/0, Cost of using 64
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Adjacency State FULL (Hello suppressed)
Index 1/3, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec