On a network using only one medium, which metric does IGRP use?

IGRP, or Interior Gateway Routing Protocol, primarily uses a composite metric for determining the best path for routing data within a network. This metric incorporates several factors, but when it comes to single medium networks, the most straightforward and primary component is hop count.

Hop count measures the number of routers (or hops) a packet must pass through to reach its destination. It provides a simple and effective way to gauge the distance to a destination; fewer hops are usually preferred as they typically imply a quicker route to the target.

While IGRP does account for other components in its composite metric, such as bandwidth, delay, reliability, and load, in contexts where only one type of medium exists, the hop count becomes the most significant factor influencing routing decisions. This ensures that routing paths are not overly complicated and rely on simple, quantitative measures of distance between nodes in the network.

Therefore, for a network utilizing a single medium, it is the hop count that stands out as the key metric used by IGRP for its routing decisions.