Exhibit.

The exhibit shows an aggregate route configuration for the network 172.21.0.0/22, which would summarize the specific networks 172.21.0.0/24, 172.21.1.0/24, and 172.21.2.0/24. For an aggregate route to be active, it must have contributing routes in the routing table. If the route is hidden, it usually means there are no contributing routes that are active or the policy applied to the aggregate does not match any of the specific routes. Therefore, the first step in troubleshooting would be to verify that there are indeed active contributing routes for the aggregate to be valid.