This. Only the first three octets (24bits) of a MAC are for the OUI (vendor ID) the remaining three are what ID the specific device, but those are totally unregistered and dynamically allocated by the vendor themselves.

This is assuming it is even a Globally Unique (OUI enforced) MAC. But to be honest, I don’t know enough about vendor registration requirements to go into those particular weeds.

Of course, I dealt with this in detail years ago. This has since been replaced with a newer 64-bit ID and some other things to keep us out of a similar situation as the IPv4 allotment space issues. But the basics still stand.

Which means the landlord has no idea how to properly segregate networks and if this is an apt, most likely EVERYONE is on the same subnet. The security issues here are astounding.