Introducing Cisco Data Center Networking (DCICN) — Question 66

Which action will a router take if it does not know the destination MAC address of a host?

Answer options

• A. Flood the packet out of every port.
• B. Drop the packet.
• C. Send an ARP request.
• D. Send a proxy ARP request.
• E. Send an ICMP unreachable message back to the source.

Correct answer: C

Explanation

The correct answer is C because when a router does not have the MAC address for a destination, it must use ARP to discover the address. Option A is incorrect as flooding is not the first step; dropping the packet (B) does not resolve the address issue; sending a proxy ARP request (D) is not standard behavior for unknown addresses; and sending an ICMP unreachable message (E) is not applicable in this context.