Route Poisoning

Route poisoning is often used in distance vector routing protocol, instructing routers that certain paths no longer exist and should be removed from the routing table. Some routing protocols such as RIP (Routing Information Protocol), utilize a maximum hop count to determine how many routes will have traffic passing through to a destination. A hop count is assigned to each route and the information is passed from router to router. When a hop count exceeds the maximum number allowed, the route is then considered unreachable. Route poisoning enables the fast removal of outdated routing information from other tables by changing the number of hop counts and delivering an updated routing table. In RIP, the maximum hop count is 15. An example of route poisoning would be changing that hop count to 16, deeming the route as unreachable so that an updated route can be sent. When a router endures route poisoning, it sends an update back to the router from which the poisoning was initiated, a process known a poison reverse. Poison reverse ensures that all segmented routers have received updated information regarding new paths.