Configuring an OSPFv3 Stub Area
Configuring a non-backbone area as a stub area can reduce routing entries in the area in an AS does not transmit routes learned from other areas in the AS or AS external routes. This reduces bandwidth and storage resource consumption.
Applicable Environment
The number of LSAs can be reduced by partitioning an AS into different areas. To reduce the number of entries in the routing table and the number of LSAs to be transmitted in a non-backbone area, configure the non-backbone area on the border of the AS as a stub area.
Configuring a stub area is optional. A stub area generally resides on the border of an AS. For example, a non-backbone area with only one ABR can be configured as a stub area. In a stub area, the number of entries in the routing table and the amount of routing information to be transmitted greatly decrease.
Note the following points when configuring a stub area:
- The backbone area (Area 0) cannot be configured as a stub area.
- If an area needs to be configured as a stub area, all the routers in this area must be configured with stub attributes using the stub command.
- An ASBR cannot exist in a stub area. External routes are not transmitted in the stub area.
Pre-configuration Tasks
Before configuring a stub area, complete the following tasks:
Configuring IP addresses for interfaces to ensure that neighboring routers are reachable at the network layer
Procedure
- Run system-view
The system view is displayed.
- Run ospfv3 [ process-id ]
The OSPFv3 process view is displayed.
- Run area area-id
The OSPFv3 area view is displayed.
- Run stub
The specified area is configured as a stub area.
- All routers in a stub area must be configured with stub attributes using the stub command.
- Configuring or deleting stub attributes will update routing information in the area. Stub attributes can be deleted or configured again only after the routing update is complete.
- (Optional) Run stub no-summary
The ABR is prevented from sending Type 3 LSAs to the stub area.
- (Optional) Run stub default-route-advertise backbone-peer-ignore
The device is configured to advertise default routes and ignore the status of the neighbors in the backbone area.
- (Optional) Run default-cost cost
The cost of the default route to the stub area is set.
To ensure the reachability of AS external routes, the ABR in the stub area generates a default route and advertises the route to the non-ABR routers in the stub area.
- Run commit
The configuration is committed.
Checking the Configurations
Run the display ospfv3 command, and you can view the OSPFv3 LSDB, including the types of LSA and link state IDs.
When Router is in a common area, there are AS external routes in the routing table. After the area where Router resides is configured as a stub area, AS external routes are invisible.