Which of the following is true about Gratuitous ARP?

• A. It can be used to detect IP address conflicts and update neighbor tables
• B. It is used to route between subnets
• C. It is used to assign IP addresses
• D. It blocks ARP requests

Answer: (A)

Gratuitous ARP is an ARP announcement a host makes about its own IP-to-MAC mapping to refresh neighbors’ ARP caches and to surface any IP-address conflicts on the local network. By broadcasting its mapping, nearby devices update their tables quickly, ensuring smooth communication, and if another device is using the same IP, the unsolicited update can reveal the conflict.

It isn’t about routing between subnets, since ARP operates only on the local broadcast domain and routing happens at a higher layer with routers. It doesn’t assign IP addresses—that’s the role of DHCP or manual configuration. It also doesn’t block ARP requests; it itself is an ARP frame used to inform others about a mapping.