Match each route-selection concept to the description that best fits it.

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Route selection in Cisco routing protocols is governed by a hierarchy of criteria that determine the best path to a destination. The first and most important factor is prefix length, which defines how specific a route is. A longer prefix length means a more specific route, and routers always prefer the most specific route available. If multiple routes have the same prefix length, the router then compares the administrative distance, which is a value representing the trustworthiness of the route source. Lower administrative distance values indicate more reliable sources, so routes with lower AD are preferred. After administrative distance is considered, if multiple routes from the same routing protocol remain, the router compares the metric values associated with those routes. Metrics vary by protocol; for example, OSPF uses cost, EIGRP uses composite metrics based on bandwidth and delay, and RIP uses hop count. The route with the lowest metric is selected as the best path. If no specific route matches a destination, routers use a default route (0.0.0.0/0) as a fallback to forward packets, ensuring connectivity even when no explicit route exists. Understanding these concepts is critical in CCNA routing questions because candidates often confuse administrative distance and metric or overlook prefix length specificity. Cisco routers strictly follow this order: prefix length, administrative distance, then metric. Misapplying these rules can lead to incorrect route selection answers. In practical networks, this hierarchy ensures predictable routing behavior and helps troubleshoot routing issues by clarifying why a particular route is chosen over others.

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