Core Issue
If a dynamic route is lost and no other alternate routes exists for that prefix in the routing table, the router stops forwarding the packets destined for that prefix. It is possible to configure a floating static route that will take over the lost dynamic route and forward traffic through it.
Resolution
Configure a default route by issuing the ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] command. Assign an administrative distance greater than the administrative distance of the dynamic routing protocol.
For more information on the administrative distance of routing protocols, refer to What Is Administrative Distance? and Specifying a Next Hop IP Address for Static Routes
