Meaning – The term metric, refers to a value, associated with a route, which is used to discriminate between multiple exits or entry points to the same autonomous system. The route with the lowest metric is preferred.
It has an unsigned value, so it can never be negative. Metrics are calculated for multiple routes to determine the best route. The route having the best metrics is usually the easiest and fastest path for delivering the packet.
The method used to calculate a metric differs from one network protocol to another. For example, Enhanced Interior Gateway Routing Protocol (EIGRP) has a metric ranging between zero and 4,294,967,295.
Example of usage – “Routing tables in routers contain only routes with the lowest metrics. There is another important network attribute called link-state, which is used together with the metric to make the final decision regarding the best path.”