Will Linux send the ARP gratuitous or ARP probe (defined in RFC 5227) I did an experiment to check if Linux will send the gratuitous ARP or ARP probe before using the target IP. The experiment scenario is as follows: There are two Linux computers, both connected to the same AP. I connected the one first and used `ifconfig wlan0 192.168.1.30` (which is another Linux computer's default IP address) to set the IP address statically. Then I use WPA_supplicant to connect the other one, and use `dhclient wlan0` to get the IP address. From sniffer, I didn't observe any gratuitous ARP or ARP probe sent from the second computer. Just wondering under what condition, will linux computer send these two ARP request? Since under the same condition, I observe that my windows computer will send the ARP Probe to solicit the IP. Thanks

Manually configuring an IP address on a device doesn't require the device to check for address conflicts. It is only if the device configures its own IP address (DHCP, etc.) that it should check for address conflicts.

You are not going to see a gratuitous ARP if you manually configure a device since the device has no way to change its (or request a new) address if it discovers a conflict. The purpose of the RFC is so that a device, configuring its own IP address, can detect if it needs to change the IP address it got. It can do that for things like DHCP, but it has no way to do that if you manually configure the address. In other words, the device has to trust that you, the human, know what you are doing, but it needs to verify that any address it comes up with on its own is not already in use.