Unsolicited ARP request
There are several possible causes:
The computer sending the traffic is infected
Example of Environmental or Application issues related with Unsolicited ARP request:
Unsolicited ARP requests from a server or appliance can be caused by applications or appliances that uses "gratuitous-arp". Gratuitous ARP is used when hosts need to update other local host ARP tables. Gratuitous ARP updates ARP tables on computer even though it is not solicited, triggering SEP events like ARP Poisoning and MAC Spoofing.
Example of Gratuitous_ARP traffic:
Ethernet II, Src: 02:02:02:02:02:02, Dst: ff:ff:ff:ff:ff:ff