When i say NULL ROUTE or BLACK HOLE ROUTING the first thing comes in your mind is what the hell is this?

What kind of interface is this NULL 0?

What is black hole in Router?

What is need of Null route in Networking?

Who used it and why?

 

In this tutorial you will get all the answer and will also learn what is Null Routing ,how to configure Null routing and why we use Null routing.

In computer network NULL ROUTE(BlackHole Route) is a network route which goes nowhere.Or you can say null route or a blackhole route is a route which divert the network in a black hole from where it never come back again.it is a type of Trash or Recycle Bin for route packets.People or company used this to drop some specific network or stop ddos attack.All traffic sent to null interface is discarded.IT person or Network Engineers used it discard traffic simply by routing it to null interface.

Note:You can filter or DROP Packet even by using ACL but Null Route is best because Access List Required More CPU overhead.

 

Here I am going to BLOCK PACKETS GENERATED FROM Router0 1.0.0.0 network for 6.0.0.0 network

 

ROUTING CONFIGURATION ON ROUTER0:

Remember we will configure NULL ROUTE on This Router.

 

Router(config)#ip route 4.0.0.0 255.0.0.0 3.0.0.2

Router(config)#ip route 5.0.0.0 255.0.0.0 3.0.0.2

Router(config)#ip route 6.0.0.0 255.0.0.0 null0

 

 ROUTING CONFIGURATION ON ROUTER1:

 

ROUTING CONFIGURATION ON ROUTER2:

 

You can see when Person seating on PC in network 1.0.0.0  trying to communicate with person in network 6.0.0.0 packets drop.

 

PC>ping 6.0.0.2

Pinging 6.0.0.2 with 32 bytes of data:

Reply from 1.0.0.1: Destination host unreachable.

Reply from 1.0.0.1: Destination host unreachable.

Reply from 1.0.0.1: Destination host unreachable.

Reply from 1.0.0.1: Destination host unreachable.

Ping statistics for 6.0.0.2:

Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

PC>