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Routing & Switching · Advanced

Remote-Triggered Black Hole (RTBH)

A DDoS mitigation technique where a BGP-signaled route sends attack traffic to a discard (Null0) next hop at the network edge.

Definition

A trigger router announces the victim prefix with a community or next hop that edge routers map to Null0, dropping traffic before it crosses the core. Source-based RTBH combines this with uRPF to drop traffic from attacking sources. Providers often accept customer blackhole requests using the BLACKHOLE well-known community 65535:666.

Example

Edge routers have ip route 192.0.2.1 255.255.255.255 Null0; triggered routes use next hop 192.0.2.1.

Exam tip

Destination RTBH drops all traffic to the victim, completing the attack's goal of denying service; source-based RTBH needs uRPF.

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