How to Aggregate Routes and Advertise via BGP

How to Aggregate Routes and Advertise via BGP

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Created On 09/26/18 13:55 PM - Last Updated 02/07/19 23:39 PM


Resolution
  • 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

bgp1.GIF

Step1: Configure the Redistribution Profiles with Destination as the Routes that need to be aggregated or summarized.

Redis-Profile.GIF

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.

Aggregate-BGP.GIF

Step 3: Configure the Redistribution Rule selecting the Redistribution Profile configured with Step1 and commit the changes. .

Redist-Rule.GIF

Verification

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

    Aggregate-Local RIB.GIF

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

    Aggregate-RIB out.GIF

owner: akawimandan



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