```html How to advertise a specific BGP route that's within an aggregated/summarized subnet.

How to advertise a specific BGP route that's within an aggregated/summarized subnet.

This KB article is to provide the procedure to advertise a specific BGP route that's within an aggregated/summarized subnet for the purpose of monitoring the path.

Combined with a static route with path monitoring, a Redistribution Profile, and BGP Redist Rule, we can achieve, Monitoring the availability of a specific path, installing that route if available, advertising that route specifically even though it’s within a larger summarized prefix, and remove the specific route and its specific advertisement if the path goes down.

  1. Create a static route with Path monitoring to monitor the path.

GUI:  Network > Virtual Routers > (Select the VR) > Static Routes > Add

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  1. Create a Redistribution Profile with filter types as “Static” and “Interface (Select the interfaces to specify the forwarding interfaces of the candidate route).” Make sure Redistribute is set to “ Redist ” in the profile.

GUI:  Network > Virtual Routers > (Select the VR) > Redistribution Profile > Add

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  1. Add the Redistribution profile to the Redist Rules in BGP and  Commit  the configuration.

GUI:  Network > Virtual Routers > (Select the VR) > BGP > Redist Rules > Add > (select the configured profile from drop down)

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Once done,  the route entries are present in the "Local RIB" of "BGP".

GUI:  Network > Virtual Routers > (Select the VR) > More Runtime Stats> BGP > Local RIB

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  1. Use Export rules to advertise the interesting routes to the peer, here I am advertising all the routes present in the local RIB. If no prefixes match is defined, the BGP will export all the routes present.

GUI:  Network > Virtual Routers > (Select the VR) > BGP > Export > Add

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After configuration and " Commit ", the entries can be seen in  RIB Out table.

GUI:  Network > Virtual Routers > (Select the VR) > More Runtime Stats> BGP > RIB Out

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  1. Creating aggregate rule:

Route aggregation is the act of combining specific routes (those with a longer prefix length) into a single route (with a shorter prefix length) to reduce routing advertisements that the firewall must send and to have fewer routes in the routing table.

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  1. Click on the "Advertise Filters" tab to create Advertise Filters. This is to exclude a specific prefix from summarization.

Define the attributes for an Advertise Filter that causes the firewall to advertise to peers any route that matches the filter. Click Add and enter a name for the Advertise Filter.. Click " OK " and  Commit  the configuration.

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  1. Now from the CLI and GUI both the summarized route and the non-aggregated route is seen in the RIB-OUT.

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  1.  On the Palo Alto Peer Router,  the advertised routes are seen in the BGP Local-RIB

GUI:  Network > Virtual Routers > (Select the VR) > More Runtime Stats> BGP > Local RIB

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