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Parameter Desc ription
Area ID An OSPF area identifier configured for a group of OSPF routers. (For
information on how to assign this identifier to a specific interface, see
chapter 3 “Configuring OSPF”.)
Type Indicates area type:
Normal An area which can send or receive external route information.
Stub An area which cannot send or receive external route
information. It relies on a single default route provided by its
A
rea Border Router (ABR) to access destinations outside of the
stub. A stub can be used to reduce the amount of topology data
that has to be exchanged over the network.
NSSA A not so stubby area cannot send but can receive external
route information. The ABR imports external routes and floods
this information to all routers within the NSSA.
An Autonomous System Boundary Router (ASBR) can import external routes and flood
this information to the entire Autonomous System.
Note:
To add an Area ID, click the string (Add New Entry). The screen can be show as
below. Specify the identifier and type in the dialog boxes at the bottom of the
screen, and press Save. To delete an Area ID, click on the Delete icon ( ) for the
required entry.
OSPF Area Range Configuration
After you configure an area identifier, you can specify a subnetwork address range that
covers all the individual networks in this area. This technique limits the amount of traffic
exchanged between Area Border Routers (ABRs) by allowing them to advertise a single
summary range. By summarizing routes, the routing changes within an area do not
have to be updated in the backbone ABRs or in other areas.
To optimize the route summary, first configure all the OSPF routers in an area so that
they fall within a contiguous address range. The route summary consists of an address
and mask, where the mask can be a Variable Length Subnet Mask (VLSM). Using