Configuring BGP Route Aggregation

Configuring BGP Route Aggregation on a device can reduce the sizes of routing tables on the peers of the device.

Context

The BGP routing table of a device 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 aggregation and routing policies enable BGP to effectively transmit and control routes.

BGP supports automatic and manual aggregation. Manual aggregation takes precedence over automatic aggregation. When using manual aggregation, you can apply various routing policies and set route attributes.

Procedure

Configuring Automatic Aggregation
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Access the BGP IPv4 view.
  ipv4-family unicast
4. Enable automatic aggregation for imported routes.
  summary automatic
  
  The summary automatic command aggregates 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 aggregates routes based on natural network segments. The command, however, cannot aggregate routes imported using the network command.
Configure manual aggregation.
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Access the BGP IPv4 view.
  ipv4-family unicast
4. Enable manual route aggregation.
  aggregate ipv4-address { mask | mask-length } [ as-set | attribute-policy route-policy-name1 | detail-suppressed | origin-policy route-policy-name2 | suppress-policy route-policy-name3 ] ^*
  
  Manual aggregation is valid for the entries in the local BGP routing table. For example, if 10.1.1.1/24 does not exist in the BGP routing table, BGP does not advertise the aggregated route after the aggregate 10.1.1.1 16 command is used to aggregate routes.