Port 520

Routing Information Protocol (RIP) is a distance-vector dynamic routing protocol standardized originally in RFC 1058. RIP uses hop count as its routing metric, with a maximum allowable hop count of 15 to prevent routing loops. Routes with a hop count greater than 15 are considered unreachable, an intentional design decision to avoid infinite loops in the network. RIP periodically broadcasts the full routing table every 30 seconds to neighboring routers, which may lead to slow convergence times when network changes occur.

Operating primarily over UDP port 520, RIP packets carry information about the entire routing table rather than incremental updates, contributing to unnecessary bandwidth usage in larger environments. The simplicity of RIP makes it easy to implement and manage, favoring networks with straightforward routing requirements and limited size. Over time, RIP has evolved, with RIP version 2 introducing support for subnet mask information, authentication, and multicast routing updates, addressing some of the limitations of the original protocol.

Despite its prevalence in earlier network deployments, RIP's limitations — such as lack of support for VLSM (in version 1), slow convergence, and susceptibility to routing loops — have led to its displacement by more sophisticated protocols like OSPF and EIGRP in larger and high-performance networks. However, RIP remains suitable for educational purposes and simple routing scenarios due to its ease of understanding and deployment.