5.7.5.2.3.1 OSPF Area Configuration
OSPF protocol broadcast messages (i.e., Link State Advertisements) are restricted by area to limit their impact on network performance. Before assigning an Area ID to a specific OSPF interface, you must first specify the Area ID in this table. Each entry in this table identifies a logical group of OSPF routers that actively exchange Link State Advertisements (LSAs) to ensure that they share an identical view of the network topology. You can configure the area as a normal one which can send and receive external Link State Advertisements (LSAs), a stubby area that cannot send or receive external LSAs, or a
Parameter | Description |
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, see4.5.6.1.5 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 Area 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. |
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An Autonomous System Boundary Router (ASBR) can import external routes and flood this information to the entire Autonomous System.
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