How do routing protocols work

Routing protocol

Routing protocols are protocols that routers use to communicate with one another. They are used to optimize the choice of route for the transmission of messages across multiple networks. The optimal route selection can be cost or bandwidth-optimized, it can take into account the load on the connection, the number of hops, the transmission speed or the real-time behavior.


Routing protocols can work with statically predefined routes or work with dynamic routing. The dynamic route assignment takes place during ongoing network operation and takes network expansions, load changes and overloads into account.

In IP networks, the data packets are delivered based on the IP addresses. The routing protocols used for this can use routing tables and create links to the destination addresses. If the routes are fixed, static routing is involved, the routes are compiled by the routing protocols, by dynamic routing. Routing protocols differ in the routing algorithms used, the metrics used, the exchange mechanisms, the convergence and the administrative effort. They can be divided into Interior Routing Protocols (IRP) and Exterior Routing Protocols (ERP). The first group includes routing protocols with distance vector algorithms such as the Gateway to Gateway Protocol (GGP), the Routing Information Protocol (RIP), the Interior Gateway Routing Protocol (IGRP) and the Enhanced Interior Gateway Routing Protocol (EIGRP) The Intermediate System to Intermediate System Protocol (IS-IS) and Open Shortest Path First (OSPF) work with link-state algorithms. The Exterior Routing Protocols (ERP) also include those that work with preferences and policies, such as the Exterior Gateway Protocol (EGP). Others, such as the Border Gateway Protocol (BGP), which uses the path-vector method, and still others, such as the Interdomain Routing Protocol (IDRP), which works with link-state algorithms.

In other wide area networks, mobile radio networks and local networks, the routing is determined by other algorithms and metrics, such as the suppression of redundant structures with the Spanning Tree Protocol or source routing.