In which scenario is Interior Gateway Routing Protocol (IGRP) utilized?

Interior Gateway Routing Protocol (IGRP) is designed specifically for use within an autonomous system, which is a collection of networks and routers under the control of a single organization. It enables routers within that system to share routing information and make routing decisions based on metrics such as bandwidth, delay, load, and reliability.

When IGRP is deployed, it efficiently manages routing within the same autonomous system, allowing routers to dynamically share routing data and to account for changes in network topology. This adaptability helps to optimize routing paths and improve overall network performance.

In contrast, the other scenarios do not align with IGRP's purpose. For instance, routers across different autonomous systems typically utilize an Exterior Gateway Protocol (EGP) like Border Gateway Protocol (BGP), and non-Cisco routers would generally not support IGRP, as it is a proprietary protocol intended for Cisco devices. Lastly, routers with static IP configurations operate independently of dynamic routing protocols, as their routes do not change automatically in response to network conditions. Thus, the use of IGRP is specifically contextualized within a single autonomous system, making it the correct choice.