RTBH

A technique that drops attack traffic by routing it to a null destination, often to blunt DDoS.

RTBH uses routing updates to steer traffic destined for a targeted address into a null route, effectively discarding it so a flood cannot reach or saturate the victim or the wider network. It can be triggered on demand and coordinated with an upstream provider to absorb a distributed denial-of-service attack closer to its source. The tradeoff is that legitimate traffic to that address is also dropped, so it sacrifices availability of the target to protect the rest. On the exam, associate RTBH with DDoS mitigation at the routing layer.