200-301 Question 297
Single answerA network administrator is troubleshooting connectivity issues in a small office. The router has multiple static and dynamic routes configured in its routing table. By default, when the router receives a packet to forward, how does it decide which route to use?
- A
It selects the route with the longest prefix match.
- B
It selects the route with the lowest administrative distance.
- C
It selects the route with the highest metric.
- D
It forwards the packet to the default gateway without checking the routing table.
Show answer and explanation
Correct answer: A
Explanation
When a router receives a packet, it looks at the destination IP address and checks its routing table for matching routes. By default, it selects the route with the longest prefix match (most specific match) to make the forwarding decision. Other factors, such as administrative distance and metrics, come into play only when multiple routes share the same prefix length.
- A. Correct.
Correct. The router uses the longest prefix match to determine the most specific route in the routing table.
- B. Incorrect.
Incorrect. While administrative distance is used to choose between different routing sources (e.g., static vs OSPF), it does not determine the actual forwarding decision for a specific packet.
- C. Incorrect.
Incorrect. The metric determines the best route within a routing protocol but does not take precedence over longest prefix match during the forwarding decision.
- D. Incorrect.
Incorrect. The router does not blindly forward packets to the default gateway; it checks the routing table first and uses the most specific match.