You configured an aggregate route of 192.168.8.0/21 and don't see it in the operational output. What could explain this?

The aggregate route of 192.168.8.0/21 may not appear in the operational output because there are no active contributing routes that match this aggregate. When an aggregate route is created, it summarizes multiple more specific routes, but if there are no more specific routes in the routing table that fall within the specified aggregate range, the aggregate route will not be generated and displayed.

In networking, an aggregate route primarily serves as a means to consolidate routing information—a way to reduce the size of the routing table by summarizing several individual routes into a single route entry. If the individual routes that would contribute to this aggregation are absent, the routing process will not form the aggregate entry.

Thus, the lack of contributing routes directly explains the absence of the aggregate route in the operational output, as the router has nothing to summarize and therefore cannot create the aggregate route entry in the routing table.