With newer Iphones and andriod handsets they have a mac address randomizer that can be used to anomously connect to access points.
originally it used the random mac to scan networks but used the hardware mac for the actual connection but this is no longer the case.
I believe in the standard the second octate has to be a specific value, I'm wonderign if there is an addon for openwrt to filter randomly generated mac adresses conforming to this standard?