Static routes are recursive in nature. Recursive means to check the route for the next hop address which is used for static route like bgp does recursive lookip for finding the next hop address. A good example of recursive lookup is MPLSVPN SP network.In SP network always PE loopback is used for customer VPNv4 routes and bgp does the recursive lookup to reach to that loopback. It means when you are going to place the static route in the routing table and the interface which is directly connected to it get down at that time the route should flush from the routing table. It usually happens but if the next hop is reachable by some other path in that case the route is not going to flush from the routing table because recursive lookup will take for finding the next hop address. This type or problem usually comes in service provider network when customer requires the redundancy. In those type scenarios try to use the static route with interface and next hop address. The main advantage of using the command is that the next hop is reachable only if the interface state is up else it will not reachable and route will be flushed from the routing table. If you configure a simple static route pointing the next hop address in that case the route is not going to flush from the table and floating route will never come in picture consequence traffic will be blackholed.