Which of the following are legitimate uses for Gratuitous ARP?

• A. Looking for duplicate IPs on local segment
• B. Advertise new IP/MAC pairing to segment
• C. Both A and B
• D. None of the above

Answer: (C)

Gratuitous ARP is an ARP packet a host sends without being asked, used to inform the local network of its IP-to-MAC mapping and to help detect conflicts on the segment.

Looking for duplicate IPs on the local segment is a legitimate use because sending an ARP for your own IP can reveal another device using that same address if a response is received, signaling an IP conflict.

Advertising a new IP/MAC pairing to the segment is also a legitimate use. When a host’s IP or MAC changes (or a new device comes online), sending a Gratuitous ARP updates neighbors’ ARP caches so traffic is correctly directed to the right MAC.

So, both looking for duplicates and announcing a new mapping are valid uses, meaning the best answer is both.