Configuring BGP Route Summarization

Configuring BGP route summarization on a device can reduce the sizes of routing tables on the peers of the device.

Usage Scenario

The BGP routing table of a router on a medium or large BGP network contains a large number of routing entries. Storing the routing table consumes a large number of memory resources, and transmitting and processing routing information consume lots of network resources. Configuring route aggregation can reduce the size of a routing table, prevent specific routes from being advertised, and minimize the impact of route flapping on network performance. BGP route summarization and routing policies enable BGP to effectively transmit and control routes.

BGP supports automatic and manual summarization. Manual summarization takes precedence over automatic summarization.

Pre-configuration Tasks

Before configuring BGP route summarization, complete the following task:

Configure basic BGP functions.

Procedure

Configure automatic route summarization.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run ipv4-family unicast
  The IPv4 unicast address family view is displayed.
4. Run summary automatic
  Automatic summarization is configured for imported routes.
  
  The summary automatic command summarizes routes imported by BGP. The routes can be direct routes, static routes, RIP routes, OSPF routes, or IS-IS routes. After this command is run, BGP summarizes routes based on natural network segments. The command, however, cannot summarize routes imported using the network command.
5. Run commit
  The configuration is committed.
Configure manual route summarization.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run ipv4-family unicast
  The IPv4 unicast address family view is displayed.
4. Configure manual summarization according to the actual networking.
  - To advertise both the summary route and specific routes, run the aggregate ipv4-address { mask | mask-length } command.
  - To advertise only the summary route, run the aggregate ipv4-address { mask | mask-length } detail-suppressed command.
  - To advertise a specific route, run the aggregate ipv4-address { mask | mask-length } suppress-policy route-policy-name command.
    
    To advertise a specific route, you can also run the peer route-policy command.
  - To generate a summary route used to detect a loop, run the aggregate ipv4-address { mask | mask-length } as-set command.
  - To set the attributes of a summary route, run the aggregate ipv4-address { mask | mask-length } attribute-policy route-policy-name command.
    
    To set the attributes of a summary route, you can also run the peer route-policy command.
    
    If as-set is set in the aggregate command and the apply as-path command is run to set the AS_Path attribute, the AS_Path attribute does not take effect.
  - To generate a summary route according to certain specific routes, run the aggregate ipv4-address { mask | mask-length } origin-policy route-policy-name command.
  Manual summarization is valid for the existing routing entries in the local BGP routing table. For example, if a route with the mask length longer than 16, such as 10.1.1.0/24, does not exist in the BGP routing table, BGP does not advertise the summary route after the aggregate 10.1.1.1 16 command is run.
5. Run commit
  The configuration is committed.

Checking the Configurations

After route summarization is configured, you can check whether the configuration is correct.

Run the display bgp routing-table [ network [ mask | mask-length ] ] command to check information about BGP summary routes.