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 50.20.200.0/24 , route 50.20.200.64/26 is a contributing route, while 50.20.200.208/28 ,50.20.200.224/28  are not.

Requirement

• Aggregate Route : 50.20.200.0/24
• Contributing route  : 50.20.200.64/26
• Non-Contributing route  50.20.200.208/28 ,50.20.200.224/28

Routing Table

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. .

Verification

• Check the Local RIB which shows the component of the Aggregated Route present in the Routing Table.

  

• RIB Out shows the Aggregated Route 50.20.200.0/24 being advertised.

  

owner: akawimandan