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OSPF Overview Configuring OSPF
page 1-10 OmniSwitch 6600 Family Advanced Routing Configuration Guide March 2005
Virtual Links
It is possible to define areas in such a way that the backbone is no longer contiguous. (This is not an ideal
OSPF configuration, and maximum effort should be made to avoid this situation.) In this case the system
administrator must restore backbone connectivity by configuring virtual links.
Virtual links can be configured between any two backbone routers that have a connection to a common
non-backbone area. The protocol treats two routers joined by a virtual link as if they were connected by an
unnumbered point-to-point network. The routing protocol traffic that flows along the virtual link uses
intra-area routing only, and the physical connection between the two routers is not managed by the
network administrator (i.e., there is no dedicated connection between the routers as there is with the OSPF
backbone).
OSPF Routers Connected with a Virtual Link
In the above diagram, Router A and Router B are connected via a virtual link in Area 1, which is known as
a transit area. See “Creating Virtual Links” on page 1-25 for more information.
Router A
Router B
Backbone
Virtual Link
Area 1
Backbone
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