How my router know that this is randomized MAC?
If you will put your mouse on "i" (circled) it will display that MAC is randomized (which is true). But how router know this?
I believe that the router can identify random MAC addresses by inspecting certain bits in the MAC.
This link is from an Android discussion, but I believe the process is standardized and other manufacturers like Apple use the same protocol.
https://source.android.com/docs/core/connect/wifi-mac-randomization-behavior
Edit - a more technical breakdown of MAC randomization -
Manufacturers are assigned MAC addresses. When you invent them, they don't exist in the databases.
The first 6 digits of the MAC correspond to the manufacturer.
The router will query to see if it exists and, if not, determine that it is random.
You can use a website like https://macvendors.com to check the manufacturer of the interface. The 6 following the part number