The process of maintaining the routing information may generate errors if there is no quick and accurate convergence between the routers. In design of complex networks may occur routing loops or loops. Routers transmit constant updates to their neighbors, if a router B receives an update of a network that has fallen, this forward this information to all its neighbors including the router B who first informed him of novelty, turn the router B will report that the network has fallen into router to form an endless loop.
Solution to routing loops
Maximum Metric:
The routing protocol allows the repetition of routing loop until the metric exceeds the maximum allowed value. For RIP the loop will only be allowed until the metric reaches 16 hops.
Split Horizon:
It is meaningless to resubmit information about a path to the direction from which came the original update. Unless the router knows another viable route to the destination will not return the interface where information was given.
Route Poisoning:
The router creates an entry in the table where he keeps the consistency of the network routers while others gradually converge correctly after a change in the topology. The downgrade is a complementary operation of the split horizon. The aim is to ensure that all routers have received information segment about the poison path.
Timers:
The timers make the routers do not implement any changes that might affect routes for a period of time. If you get an update with a better metric to the network inaccessible, the router updates and deletes the timer. If you will not receive optimal changes by dropping the network to spend the waiting time.