Thanks a lot for your great explanation, Lazaros.
Do you know if cisco switches have got the same default behavior with gratuitous arp packets? I means, I have just replaced a Cisco 2955 switch for a new Cisco 3850, and since then users complain about the refreshing arp time when changing damaged IP devices. I have found that in older Cisco2955 there is not any specific arp command, so I suppose that it must allow gratuitous arp packets as default, while in Cisco 3850 there is a global command “ip gratuitous arp non-local”