Qtech QSW-3900-24-SFP-AC [98/245] Ospf router types

Qtech QSW-3900-48-SFP-DC [98/245] Ospf router types
QTECH Software Configuration Manual
8-97
OSPF router types
8.1.2.3 Backbone area and virtual links
Each AS has a backbone area, which is responsible for distributing routing information between
none-backbone areas. Routing information between non-backbone areas must be forwarded by the backbone area.
Therefore, OSPF requires that :
· All non-backbone areas must maintain connectivity to the backbone area.
· The backbone area itself must maintain connectivity.
In practice, due to physical limitations, the requirements may not be satisfied. In this case, configuring
OSPF virtual links is a solution.
A virtual link is established between two area border routers via a non-backbone area and is configured on
both ABRs to take effect. The area that provides the non-backbone area internal route for the virtual link is a transit
area.
In the following figure, Area 2 has no direct physical link to the backbone area 0. Configuring a virtual link
between ABRs can connect Area 2 to the backbone area.
Virtual link application 1

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