Virtual Links

In the situation when a new area is introduced that does not have a direct physical attachment to the backbone, a virtual link is used.

A virtual link provides a logical path between the ABR of the disconnected area and the ABR of the normal area that connects to the backbone. A virtual link must be established between two ABRs that have a common area, with one ABR connected to the backbone. The following figure illustrates a virtual link.

Note

Note

Virtual links cannot be configured through a stub or NSSA area.
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Virtual Link Using Area 1 as a Transit Area
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Virtual links are also used to repair a discontiguous backbone area. For example, in the following figure, if the connection between ABR 1 and the backbone fails, the connection using ABR 2 provides redundancy so that the discontiguous area can continue to communicate with the backbone using the virtual link.

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Virtual Link Providing Redundancy
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