An OSPF virtual link is a link between two OSPF virtual neighbor endpoints. Each complete OSPF virtual link connects two OSPF virtual neighbor endpoints.
As clarified in Virtual link uses, virtual links serve two purposes:
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Link an OSPF area that does not have a physical connection to the backbone area (Area 0).
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Patch the backbone in case discontinuity of Area 0 occurs.
Figure 1. Virtual link uses 
