I don't know what's the model of the 2600 you have. IGRP on 2611 is supported in 12.2(11)T7 or earlier versions. It appears you may have to downgrade the code to 12.2 or earlier version to enable IGRP. But, check the software advisor tool to pick the right image.
BTW, is there any specific reason why you want to run IGRP. You can consider EIGRP, successor to IGRP, and there are lot of similarities between them.
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
worked as a Senior Engineer with the Routing P...
In this session you can learn more about Layer 3 multicast and the best
practices to identify possible threats and take security measures. It
provides an overview of basic multicast, the best security practices for
use of this technology, and recommendati...