Which routing protocol uses hop count as its primary metric?

The routing protocol that uses hop count as its primary metric is RIP, which stands for Routing Information Protocol. RIP is one of the simplest and oldest routing protocols, functioning under the distance-vector protocol classification. In RIP, hop count represents the number of routers (hops) a packet must pass through to reach its destination. The maximum hop count allowed is 15, meaning that any path costing 16 hops is considered unreachable.

This focus on hop count makes RIP easy to configure and understand, but it also limits the complexity and scalability of the routing decisions, as it does not take into consideration other factors such as latency or bandwidth. This simplicity can lead to inefficiencies in larger or more intricate networks.

In contrast, the other options utilize different metrics or a combination of metrics. OSPF, for example, uses cost based on link bandwidth, while IGRP and EIGRP take into account multiple factors for routing decisions, making them more sophisticated and adaptable in various network environments.