I wonder how it detected it. Perhaps the randomly-generated ones are mostly in invalid/unassigned MAC space?

There is a "local bit" in MAC addresses per RFC 7042, so MAC addresses that have their second character as E, A, 2 or 6 are "local" which effectively means "randomly selected by software". So my current macOS selected MAC address of 16:6a:d2:20:e6:eb is "local" due to the second digit in the address being 6

	▲	bapak a day ago \| parent \| next [-]
		Oof, I wonder if this is the reason why I constantly have issues with my M1 Mac connecting to cafe hotspots. Regularly I find places that let me connect and then kick me off less than a minute later.
	▲	boston_clone a day ago \| parent \| prev [-]
		I had no idea about this; generally i thought it was done by OUI like the GP suggested - they have a small cached table of valid OUIs and warn on prefixes not in that subset. Thanks for sharing!