Each router sends information every 30 sec. If a router does not receive an update from another router for 180 sec, it marks routes served by that router as unusable. All routing table entries are removed after 240 sec. IP Routing protocols are divided into two classes. The routing tables contain a list of known routers, the addresses they can reach, and a cost metric.
Protocols push multicast traffic to all points on a network.
It requires separate unicast and multicast tables and does not scale well.