The Interior Gateway Routing Protocol (IGRP) is a distance-vector routing protocol developed by Cisco for use within an autonomous system. It helps routers communicate and share information about the best paths for data packets within a local network. IGRP uses metrics such as bandwidth, delay, load, and reliability to determine the most efficient route. IGRP is designed to support larger networks and can handle up to 255 hops, making it suitable for complex topologies. Although it has been largely replaced by the more advanced Enhanced Interior Gateway Routing Protocol (EIGRP), IGRP laid the groundwork for modern routing protocols.