If any routing table entries are misconfigured though a misconfiguration or through learned routes that do not accurately reflect the topology, routing loops can occur, leading to a path through the internetwork for a network ID that loops back onto itself. When a link or router fails, the internetwork must reconfigure itself, and information in routing tables must be updated. The time it takes for the internetwork to reconverge is known as the convergence time. Non-Internet backbone routing protocols are based either on a distance vector or link state technology. Distance vector-based routing protocols periodically advertise routes in their routing tables.
Periodic advertisement contains a hop count and a vector.
Information exchanged between distance vector-based routers is unsynchronized and unacknowledged. Distance vector-based routing protocols are simple router advertisement processes easy to understand and easy to configure. Disadvantages of distance vector-based routing protocols include large routing tables, high network traffic overhead, poor scalability and high convergence time. Link state-based routing protocols exchange link state advertisements LSAs which consist of a router's attached network IDs and interface costs. Link state routers build a database of LSAs and calculate optimal routes, which are then added to the routing table.