Verilink WANsuite 6x30 (34-00315.B) Product Manual - Manual (Page 149)

V T 1 0 0 I n t e r f a c e 4-51
routers and networks form the protocol's topological database.
Values: Yes, No
Default: No
Virtual Link Table Screen
To permit maximum flexibility, OSPF allows the configuration of virtual links
to enable the backbone area to appear contiguous despite the physical reality.
In OSPF, the backbone is defined as an Area ID of 0.0.0.0. This backbone
cannot be disconnected in any way or some areas of the Autonomous System
become unreachable. This is because all inter-area traffic must go through the
backbone. In fact, the backbone is responsible of all inter-area routing
information distribution.
It is possible that an area cannot be connected directly to the backbone. In this
case a virtual link is used. To establish or maintain the connectivity of the
backbone, virtual links can be configured through non-backbone areas.
Basically, virtual links are used to connect components that are otherwise not
connected to the backbone.
A virtual link is treated by OSPF as a point-to-point unnumbered network
joining two area border routers. The virtual link must be configured in both of
the area border routers.
A virtual link is defined by the following two parameters:
•
The Router ID of the virtual link’s other endpoint
• The non-backbone area the virtual link goes through.
Figure 4.48 Virtual Link Table Screen