OSPF Virtual Links

OSPF Virtual Links
In OSPF there is a basic requirement while designing a network with multiple areas that every area is directly connected to backbone area 0. Virtual link comes when some area e.g. area-2 in figure is not directly connected to area 0. There is area-1 in between area-2 and backbone area-0, so in this case communication between area-0 and area-2 is not possible. To make communication between these areas you need to create virtual-links.

How to create OSPF Virtual-links:
For creating virtual- links you need to connect the area which is not directly connect to area-0 to area which is directly connected to area-0. In figure you can see that Area-2 is not directly connect to area-0 to connect this area-2 to area-0 you need to create a virtual link between area-1 & area-2 by using commands as
R2(config)#router ospf 1
R2(config-rtr)#area 1 virtual-link

R3(config)#router ospf 1
R3(config-rtr)#area 1 virtual-link

Where and are router IDs.

OSPF Virtual link configuration Example
Follow this link for OSPF virtual link configuration example on Cisco router.

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