Network routing protocols are algorithms and communication standards that allow routers to dynamically discover network paths, share routing information, and make forwarding decisions across interconnected networks. They operate at Layer 3 of the OSI model and form the intelligence layer that enables packets to traverse complex network topologies efficiently. Routing protocols are classified into interior gateway protocols (IGPs) for intra-domain routing within autonomous systems, and exterior gateway protocols (EGPs) for inter-domain routing between autonomous systems. A critical distinction: administrative distance determines which protocol's route wins when multiple protocols advertise the same destination, while metrics within each protocol determine the best path among routes learned by that protocol alone.