This article is all about how to configure null routing on cisco routers in cisco packet tracer. In other words, null o routing is also known as black hole routing configuration over the cisco routers. In computer networking, a null route or black hole route is a network route that goes nowhere. Matching packets are dropped (ignored) rather than forwarded, acting as a kind of very limited firewall. Null routing is acting as a black hole on the routers because it sends unwanted packets from a certain network to black hole without reaching them to the receiver. it diverts all the packets to the black hole from where it never come back again. It is a type of trash or Recycles Bin for route packets. Basically, companies used this to drop some specific network to stop the DDOS attack. All the traffic from an unwanted network is sent to the null interface is discarded. Network admin used it to discard traffic simply by routing it to the null interface.