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Routing & Switching · Foundational

Metric

A protocol-specific value expressing the cost of a path; within one routing protocol the lowest metric route is preferred.

Definition

Each routing protocol computes metrics differently: RIP counts hops, OSPF and IS-IS sum interface costs, EIGRP uses a composite of bandwidth and delay, and BGP uses path attributes rather than a single metric. Metrics are only compared between routes learned from the same protocol. Equal metrics can result in equal-cost multipath load sharing.

Example

An OSPF route with cost 20 is preferred over another OSPF route to the same prefix with cost 30.

Exam tip

Metrics are compared only after longest match and administrative distance; never compare a RIP hop count to an OSPF cost.

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