What issue does poisoned reverse help solve in RIP?

Poisoned reverse is a technique used within the Routing Information Protocol (RIP) to combat the problem of routing loops. When a router receives an update indicating that a certain route is no longer valid (for instance, if a network segment goes down), it will propagate this information to its neighbors. However, to prevent a situation where the neighbor router believes it can still reach the destination through the router that declared the route as invalid, the router sends back an update indicating that it has a route to that destination but with an infinite metric. This effectively "poisons" the route, signaling to the neighboring router that it should no longer use that route.

By implementing poisoned reverse, networks can prevent incorrect routing information from circulating back and forth between routers, which can lead to confusion and endlessly looping packets. This mechanism is particularly beneficial in environments where there are frequent changes in the network topology, as it aids in quickly reconverging routers on valid paths. Thus, the primary role of poisoned reverse is to mitigate the risk of routing loops, ensuring the stability and efficiency of the routing process within RIP.