OSPF using virtual-link with GRE-tunnel

All areas in an Open Shortest Path First (OSPF) autonomous system must be physically connected to the backbone area (Area 0). In some cases, where this is not possible, you can use a virtual link to connect to the backbone through a non-backbone area. You can also use virtual links to connect two parts of a partitioned backbone through a non-backbone area. The area through which you configure the virtual link, known as a transit area, must have full routing information. The transit area cannot be a stub area. This example examines the OSPF database in a virtual link environment.

Let's begin:

[*] Before the GRE tunnel be created

R3# sh ip ospf neighbor

...
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           1   FULL/DR         00:00:37    172.16.0.2      FastEthernet0/1

R3# sh ip route ospf

<empty>

R1# sh ip ospf neighbor

...
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           1   FULL/BDR        00:00:30    192.168.0.2     FastEthernet0/0

R1 #sh ip route ospf   

<empty>

[The OSPF using GRE tunnel like VLINK]

R3# sh ip route ospf

     100.0.0.0/30 is subnetted, 1 subnets
O IA    100.0.0.0 [110/11112] via 172.16.0.2, 00:00:51, FastEthernet0/1
     192.168.0.0/30 is subnetted, 1 subnets
O IA    192.168.0.0 [110/2] via 172.16.0.2, 00:00:51, FastEthernet0/1
     30.0.0.0/24 is subnetted, 1 subnets
O IA    30.0.0.0 [110/11113] via 172.16.0.2, 00:00:41, FastEthernet0/1

R3# ping 30.0.0.1 so f0/1

...
Sending 5, 100-byte ICMP Echos to 30.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 172.16.0.3 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/35/44 ms

R1# sh run int tun 0

...
Current configuration : 122 bytes
!
interface Tunnel0
 ip address 100.0.0.1 255.255.255.252
 tunnel source 192.168.0.1
 tunnel destination 192.168.0.2
end

R1# sh run | s router ospf

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 30.0.0.0 0.0.0.255 area 0
 network 100.0.0.0 0.0.0.3 area 0
 network 192.168.0.0 0.0.0.3 area 10

[*] Make usage of the KISS principle

!!!!!

!.!..

 ....!

biOos