|  | 12.4 | IGRP
| 12.4.1 | Key characteristics of IGRP
IGRP is a distance-vector routing protocol developed by Cisco. IGRP sends routing updates at 90 second intervals, advertising networks for a particular autonomous system. Some of the IGRP key design characteristics emphasize the following: versatility that enables it to automatically handle indefinite, complex topologies flexibility for segments that have different bandwidth and delay characteristics scalability for functioning in very large networks The IGRP routing protocol uses a combination of variables to determine a composite metric. Those variables include: bandwidth delay load reliability