A network engineer has configured a router that has multiple routes to overlapping network destinations in its routing table. When the router receives a packet to forward, what is the first criterion it uses to select the best route?
The route with the lowest routing protocol metric
The route learned via OSPF over one learned via EIGRP
Routers make forwarding decisions by first looking for the most specific route that matches the destination IP address in the routing table, which means the route with the longest prefix length (smallest subnet). This process is known as longest prefix match. Administrative distance and routing protocol metrics are used only when multiple routes have the same prefix length. Therefore, the router's first criterion is the specificity of the network match.
Administrative distance is a measure of trustworthiness of the routing source, used when choosing between routes with the same prefix length from different routing protocols. Routing protocol metrics are used to compare routes from the same protocol. The type of routing protocol (such as OSPF or EIGRP) is considered based on administrative distance, not the protocol preference itself.
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Cisco CCNA 200-301
IP Connectivity
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