In the world of IP routing, a black hole is also a term with a negative connotation and trust me, no one wants traffic going there unless you are under a DDoS attack..
In its simplest form, a black hole exists on a network when a router directs network traffic to a destination that just “throws away” the traffic. The classic interface used on a Cisco router to do this is the null0 interface. Black hole routes can help you by dropping malicious traffic if you’re under attack, such as in the case of DDoS attacks or worm attacks.
A Cisco IOS router also has an interface called null0. When traffic goes to that interface, the router just discards it. Thus, the null interface on the Cisco router is the “black hole. Read more on Tech Republic. I found it interesting although this is certainly not my area of expertise.
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