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IP R
OUTING
C
OMMANDS
4-349
Command Usage
• An area ID uniquely defines an OSPF broadcast area. The area ID 0.0.0.0
indicates the OSPF backbone for an autonomous system. Each router
must be connected to the backbone via a direct connection or a virtual
link.
• Set the area ID to the same value for all routers on a network segment
using the network mask to add one or more interfaces to an area.
• Be sure to include the primary address for an interface in the network
area, otherwise, OSPF will not operate for any secondary addresses
covered by the command.
• An interface can only be assigned to a single area. If an address range is
overlapped in subsequent network area commands, the router will
implement the address range for the area specified in first command, and
ignore the overlapping ranges in subsequent commands. However, note
that if a more specific address range is removed from an area, the
interface belonging to that range may still remain active if a less specific
address range covering that area has been specified.
• This router supports up to 64 OSPF router interfaces, and up to 16 total
areas (either normal transit areas, stubs, or NSSAs).
Example
This example creates the backbone 0.0.0.0 covering class B addresses
10.1.x.x, and a normal transit area 10.2.9.0 covering the class C addresses
10.2.9.x.
Console(config-router)#network 10.1.0.0 255.255.0.0 area 0.0.0.0
Console(config-router)#network 10.2.9.0 255.255.255.0 area 10.1.0.0
Console(config-router)#