Comment by cesarb

This reminds me of back when Apple sold WiFi access points (they were high-quality, but a pain to administer since they required running a Windows-only or a MacOS-only executable). I tried running arpwatch for a while on a network which had one of these, and gave up, since the MAC address for any Apple machine on the network was constantly bouncing between the real machine and the access point. Apparently, whenever an Apple desktop went to sleep, that WiFi access point proxied ARP and mDNS requests for it, much like what's described on this post (but it did that by default, with no configuration required to enable it).