Route Poisoning
Key Points
- Marks failed routes as unusable
- Used in distance-vector routing
- Helps prevent routing loops
- Supports faster recovery after topology changes
Definition
Route Poisoning is a routing technique that advertises a failed route with an invalid metric so routers treat it as unreachable. It helps prevent loops and speed convergence.
Concept
Route Poisoning is a networking term used in distance-vector routing to mark failed paths as unreachable through an advertised invalid metric. It exists to reduce loops and improve reaction to failures. It is used in routed networks and routing protocols that rely on neighbor updates. The technique helps neighboring routers quickly stop forwarding traffic over broken paths.
Explainer
Route Poisoning is a routing control technique in which a failed route is advertised with an invalid or very poor metric so neighboring routers stop using it. It works by explicitly informing the network that a path is no longer usable, which helps prevent routers from believing in stale reachability information. It is used in distance-vector routing environments and related protocols that rely on route advertisements. Constraints include protocol support, metric conventions, topology scale, and the timing of update propagation. Failure modes include delayed withdrawal, incorrect poisoning scope, route flapping, and loops if the poisoned information does not reach all relevant neighbors. Tradeoffs involve faster failure recognition versus extra control-plane messaging and simpler loop prevention versus protocol-specific complexity. Route Poisoning matters because routing systems need a way to stop using failed paths quickly and safely. Cross-industry relevance is present in network engineering, service provider routing, and legacy routed systems.