How to Aggregate Routes and Advertise via BGP
- Route aggregation allows you to combine groups of routes with common addresses into a single entry in the routing table. This decreases the size of the routing table as well as the number of route advertisements sent by the routing device.
- Route aggregation works when it has one or more contributing route.
- A contributing route is an active route that is a more specific match for the aggregate destination.
- Example: for the aggregate destination 188.8.131.52/24 , route 184.108.40.206/26 is a contributing route, while 220.127.116.11/28 ,18.104.22.168/28 are not.
- Aggregate Route : 22.214.171.124/24
- Contributing route : 126.96.36.199/26
- Non-Contributing route 188.8.131.52/28 ,184.108.40.206/28
Step1: Configure the Redistribution Profiles with Destination as the Routes that need to be aggregated or summarized.
Step 2: Configure the Aggregate section with the aggregated route. This route would be a summary of the Destinations configured in Redistribution Profile and advertised to the EBGP neighbor.
Step 3: Configure the Redistribution Rule selecting the Redistribution Profile configured with Step1 and commit the changes. .
- Check the Local RIB which shows the component of the Aggregated Route present in the Routing Table.
- RIB Out shows the Aggregated Route 220.127.116.11/24 being advertised.