Introducing Cisco Data Center Networking (DCICN) — Question 6

What action does a switch take if the destination MAC address is unknown?

Answer options

• A. Discard frame
• B. Send ICMP unreachable message to source
• C. Flood packet on all ports
• D. Compare destination IP address against an ACL to determine if it is permitted
• E. Send gratuitous ARP on all ports and wait for reply before forwarding

Correct answer: C

Explanation

The correct answer is C because when a switch does not recognize the destination MAC address, it floods the packet to all ports to find the correct destination. Options A, B, D, and E are incorrect as they describe actions not taken by a switch in this scenario, such as dropping the frame, sending ICMP messages, or checking ACLs.