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| 6.8 |  | Virtual Links |
| 6.8.3 |  | Virtual link configuration example |

In Figure Area 3 does not have a direct physical connection to the backbone, Area 0, which is an OSPF requirement. This is because the backbone is a collection point for LSAs. ABRs forward summary LSAs to the backbone, which in turn forwards the traffic to all areas. All interarea traffic transits the backbone.

To provide connectivity to the backbone, a virtual link must be configured between R2 and R1. Area 1 will be the transit area and R1 will be the entry point into Area 0. R2 will have a logical connection to the backbone through the transit area.

Both sides of the virtual link must be configured, as follows:

- R2(config-router)#area 1 virtual-link 10.3.10.5 – With this command, Area 1 is defined to be the transit area and the router ID of the other side of the virtual link is configured.
- R1(config-router)#area 1 virtual-link 10.7.20.123 – With this command, Area 1 is defined to be the transit area and the router ID of the other side of the virtual link is configured.