An OSPF router learns a route with metric 20 and another OSPF route to the same destination with metric 30. The prefix length is the same. Which path is preferred?

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OSPF (Open Shortest Path First) is a link-state routing protocol that uses cost as its metric to determine the best path to a destination. The cost metric in OSPF is typically based on the bandwidth of the links along the path, with lower cost values indicating preferred routes. When multiple OSPF routes to the same destination prefix exist, the router compares their metrics to select the best path. The decision process in OSPF routing involves comparing the metrics of candidate routes learned from the same routing protocol. Since both routes in the question are OSPF routes with the same prefix length, the router selects the route with the lower metric value, which is 20 in this case. Administrative distance does not influence the choice here because both routes come from the same protocol, so metric is the sole deciding factor. A common exam trap is confusing administrative distance with metric or assuming that differing metrics cause routes to be rejected. In reality, OSPF always prefers the route with the lowest metric and installs it in the routing table. Understanding this distinction is critical for CCNA candidates, as it reflects practical routing behavior and prevents misinterpretation of OSPF route selection in Cisco devices.

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