A null route or blackhole route is a route for an IP address that goes nowhere. The reason for creating a null route for your IP address is to prevent your server from receiving or sending any data over the Internet.
The null route is activated for the server’s IP address if DDoS attacks are detected. Using this, the server can be temporarily disconnected from the Internet to prevent harm to the entire infrastructure and bandwidth over-usage for a particular server.
Normal Internet connectivity is restored to the server automatically once the DDoS attack stops.
