Command Usage
• An area ID uniquely defines an OSPF broad cast are a. The area ID 0.0.0.0
indicates the OSPF backbone for an autonomous system. Each router (which
is not already part of the backbone) must be connected to th e backbone via a
direct connection or a virtual link.
• Set the area ID to the same value for all routers on a network s egme nt usin g
the network mask to add one or more in terfaces to an area.
• Be sure to include the primary address for an interf ace in the ne twork are a,
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 the last command, and ig nore t he
overlapping ranges in subsequent commands . Howeve r, note t hat if a more
specific address range is removed from an area, the interface belon ging to
that range may still remain active if a less specific address range covering that
area has been specified.
• If an address range is overlapped in subsequent network area commands, the
router will use the network area with the addres s range th at most cl osely
matches the interface address. Also, note that if a more spe cific a ddress
range is removed from an area, the interface belonging to that range may st ill
remain active if a less specific address range covering that area has b een
specified.
• This router supports up to 64 OSPF router interfaces, and up to 16 to ta l area s
(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)#
area stub
This command defines a stub area. To remove a stub, use the
no
form without the
optional keyword. To alter the summary attribute, use the
no
form with the summary
or no-summary keyword.
Syntax
[no] area area-id stub [summary | no-summary]
• area-id - Identifies the stub area.
(The area ID must be in the form of an IPv 4 address .)
• summary - Makes an Area Border Router (ABR ) send a summar y link
advertisement into the stub area.
• no-summary - Stops an Area Border Router (ABR) from send ing a
summary link advertisement into the stub area.
42-27
Open Shortest Path First (OSPF)
42