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In networking, a hop count is the total number of intermediate devices such as routers through which a given piece of data must pass between the source and destination, instead of flowing directly over a single wire. Along the data path, each router forms a hop, with data moving from one source to another. The hop count is considered a basic measurement of the distance in a given network. In other words, it gives an approximate measure of the distance between two given hosts.
A hop count of X equates to having X gateways between the source host and destination host. In a given a path, as each device capable of receiving the data packets receives the packets, the device not only modifies the packet but also increases the hop count by one. The device also compares the hop count against a defined time to live limit and eliminates the packet if the hop count is high. This helps packets in moving around the network, especially in the case of routing errors. In a network, each point-to-point link is technically a hop, and hop count pertains only to the number of network devices between the start and end nodes. Hop count only considers devices which perform routing. As a result, routers and firewalls which perform routing are all considered in hop counts. Repeaters, firewalls which are not routers, hubs and switches are not considered in hop counts, as they do not route.
A hop count is not helpful in obtaining the optimum network path, as it does not consider the load, speed, reliability or latency involved in the network. Certain routing protocols such as Routing Information Protocol consider hop count as the sole metric in their evaluation.