Configuring Route Summarization

When a large-scale OSPF network is deployed, you can configure route summarization to reduce routing entries.

Context

Route summarization on a large-scale OSPF network reduces routing entries, minimizes system resource consumption, and maintains system performance. In addition, if a specific link frequently alternates between Up and Down, the links not involved in the route summarization will not be affected, which prevents route flapping and improves network stability.

Procedure

Configuring ABR Route Summarization
1. Run system-view
  The system view is displayed.
2. Run ospf [ process-id ]
  The OSPF view is displayed.
3. Run area area-id
  The OSPF area view is displayed.
4. Run abr-summary ip-address mask [ [ advertise | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] | [ generate-null0-route ] ] ^* | [ not-advertise | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] ] ^* | [ generate-null0-route | [ advertise ] | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] ] ^* ]
  ABR route summarization is configured.
5. Run commit
  The configuration is committed.
Configure ASBR route summarization.
Perform the following steps on the OSPF ASBR:
1. Run system-view
  The system view is displayed.
2. Run ospf [ process-id ]
  The OSPF process view is displayed.
3. Run asbr-summary ip-address mask [ [ not-advertise | generate-null0-route ] | tag tag-value | cost cost-value | distribute-delay interval ] ^*
  ASBR route summarization is configured.
4. Run commit
  The configuration is committed.
  
  After route summarization is configured, the routing table on the local OSPF router remains the same. The routing table on another OSPF router, however, contains only one summarized route, no specific route. This summarized route is not removed until all specific routes are interrupted.