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How does a router decide which route to use when multiple paths are available?
Asked on Dec 03, 2025
Answer
Routers use routing protocols and metrics to determine the best path when multiple routes are available. The decision is based on factors such as administrative distance, metric values, and specific protocol algorithms like those used in OSPF or BGP.
Example Concept: Routers evaluate multiple routes using routing tables and protocol-specific metrics. The route with the lowest administrative distance is preferred. If multiple routes have the same administrative distance, the router will use the metric (e.g., hop count in RIP, cost in OSPF, or path attributes in BGP) to select the optimal path. This ensures efficient and reliable packet delivery by prioritizing routes based on predefined criteria.
Additional Comment:
- Administrative distance is a measure of trustworthiness for a route source, with lower values being more preferred.
- Metrics vary by protocol: OSPF uses cost, RIP uses hop count, and BGP uses path attributes like AS path length.
- Routers maintain routing tables that dynamically update as network topology changes, ensuring optimal path selection.
- Load balancing can occur if multiple paths have equal cost, distributing traffic across them.
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