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OUTING
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CLI - This example configures a virtual link from the ABR adjacent to
area 0.0.0.4, through a transit area to the neighbor router 10.1.1.252 at the
other end of the link which is adjacent to the backbone.
Configuring Network Area Addresses
OSPF protocol broadcast messages (i.e., Link State Advertisements or
LSAs) are restricted by area to limit their impact on network performance.
A large network should be split up into separate OSPF areas to increase
network stability, and to reduce protocol traffic by summarizing routing
information into more compact messages. Each router in an area shares
the same view of the network topology, including area links, route
summaries for directly connected areas, and external links to other areas.
Command Usage
• Use the Network Area Address Configuration page to specify an Area
ID and the corresponding network address range. Each area identifies
a logical group of OSPF routers that actively exchange LSAs to ensure
that they share an identical view of the network topology.
• Each area must be connected to a backbone area. This area passes
routing information between other areas in the autonomous system.
The default value 0.0.0.0 is used as the Area ID for the backbone. All
routers must be connected to the backbone, either directly, or through
a virtual link if a direct physical connection is not possible.
• An area initially configured via the Network Area Address
Configuration page is set as a normal area (or transit area) by default.
A normal area can send and receive external Link State Advertisements
(LSAs). If necessary, you can use the Area Configuration page to
configure an area as a stubby area that cannot send or receive external
LSAs, or a not-so-stubby area (NSSA) that can import external route
information into its area (page 3-291).
Console(config-router)#area 0.0.0.0 virtual-link 10.1.1.2523-160
Console(config-router)#