200-301 Question 296
Single answerA network administrator has configured a router with multiple static routes and enabled a dynamic routing protocol. When the router receives a packet, how will it make a forwarding decision by default?
- A
It prefers the route with the lowest administrative distance.
- B
It prefers the route with the longest subnet mask match.
- C
It forwards the packet to the default route if available.
- D
It uses equal-cost load balancing to forward the packet.
Show answer and explanation
Correct answer: B
Explanation
When a router receives a packet, it examines the destination IP address and checks the routing table for the most specific route, determined by the longest subnet mask match. While other factors like administrative distance and default routes play a role in certain scenarios, the longest prefix match is the default method for forwarding decisions.
- A. Incorrect.
This is incorrect because while the administrative distance influences route selection between routing protocols, the router first looks at the longest subnet mask match when making a forwarding decision.
- B. Correct.
This is correct because, by default, a router makes forwarding decisions based on the longest prefix match in the routing table, which ensures the most specific route is selected.
- C. Incorrect.
This is incorrect because the default route is used only if no other more specific match exists in the routing table.
- D. Incorrect.
This is incorrect because equal-cost load balancing applies only when there are multiple routes with the same cost and the same prefix length in the routing table.