Interior gateway routing protocol (IGRP) is a proprietary distance-vector routing protocol invented by Cisco, used by routers to exchange routing data within an autonomous system. IGRP was created to overcome the limitations of RIP when used within large networks. IGRP's metrics include bandwidth, load, delay, and relability. The maximum hop count of IGRP-routed packets is 255.
EIGRP it's successor, is a hybrid routing protocol, combining link-state and distance-vector.
See also Routing.