Large volumes of Gratuitous ARP messages is usually a sign of

• A. Physical breakage in line
• B. IP address conflict
• C. Router reboot
• D. DNS misconfiguration

Answer: (A)

Gratuitous ARP is used by hosts to announce their own IP-to-MAC mapping on the local network and to detect if another device is using the same IP. When you see large volumes of Gratuitous ARP, it points to a problem on the segment that keeps triggering devices to re-announce or refresh their mappings. A physical break or line fault often causes the link to flap—interfaces go up and down or reset repeatedly—which makes devices repeatedly reinitialize neighbor discovery and broadcast Gratuitous ARP messages. That burst of ARP activity on the LAN is what you’d expect to accompany a deteriorating or unstable physical connection.

An IP address conflict can trigger Gratuitous ARP as devices probe to see if the claim on an IP is valid, but it typically doesn’t produce a broad flood of Gratuitous ARP across many devices. DNS misconfiguration and a router reboot don’t inherently cause a sustained surge of Gratuitous ARP on the network in the same way a flaky physical link does.