This maybe sound stupid. On my wifi network (Belkin RT3200 OpenWrt SNAPSHOT r20705-1722e23ffc) I see a device which i can not find nor do i know which device it could be.
It seems to connect to 2.4G correctly, it shows its MAC and gets an IP address. I guess at some point in time it was correctly configured as it gets authenticated.
Searching for a vendor based on the MAC address returns nothing. So that's a dead end.
Does anybody have suggestions how to track this thing down?
First guess is a device with “private mac” function like a iOS (apple) device.
If that function (often by default!) is activated in the client it makes up a mac every time it finds a new network.
Yes that is a "local" MAC (second digit is 2, 6, A, or E) which usually means a phone or tablet has generated a random MAC to improve user privacy. Apple was the first to do this but late-model Android now does as well.
That's interesting. I didn't know that.
I don't own any Apple devices but do own a couple, not that recent, Androids. Is that feature something I can check for on the device or is that built-in?
On iOS it is an on/off switch in the wifi info settings. I guess Android has the same checkbox somewhere.