A black hole static route is a route with an invalid next hop, and the device drops data packets destined for this network.
While the router aggregates or injects routes to other routers, the router does not have a path to the aggregated destination. In such cases, the result is a black hole and a routing loop. To avoid routing loops, configure a black hole static route to the destination the router is advertising.
You can configure a preference value for a black hole route. However, you must configure that preference value appropriately so that when you want to use the black hole route, it is elected as the best route.
Before you add a black hole static route, perform a check to ensure that no other static route to that identical destination is enabled. If such a route exists, you cannot add the black hole route and the system displays an error message.
If you enable a black hole route, you cannot add another static route to that destination. You must first delete or disable the black hole route before you add a regular static route to that destination.
Only black hole routes that belong to the static type protocol are supported. An inter-VRF black hole route is not installed in the routing table of the destination VRF on the same switch.