3.3.m Implement and troubleshoot loop prevention mechanisms

3.3.m [iii] Route poisoning

http://en.wikipedia.org/wiki/Route_poisoning

Route poisoning is a method to prevent a router from sending packets through a route that has become invalid within computer networks. Distance-vector routing protocols in computer networks use route poisoning to indicate to other routers that a route is no longer reachable and should not be considered from their routing tables. Unlike the split horizon with poison reverse, route poisoning provides for sending updates with unreachable hop counts immediately to all the nodes in the network.