Routing loop

Thus, whenever traffic for C arrives at either A or B, it will loop endlessly between A and B, unless some mechanism exists to prevent that behaviour.

In a simple reachability protocol, such as EGP, the routing loop will persist forever.

In a naive distance-vector protocol, such as the routing information protocol, the loop will persist until the metrics for C reach infinity (the maximum number of routers that a packet can traverse in RIP is 15.

[2] Newer distance-vector routing protocols like EIGRP, DSDV, and Babel have built-in loop prevention: they use algorithms that assure that routing loops can never happen, not even transiently.

Older routing protocols like RIP and IGRP do not implement the newest forms of loop prevention and only implement mitigations such as split horizon, route poisoning, and holddown timers.