A MAC address, also called a physical address, hardware address, or link address, is written inside the hardware when produced by a network device manufacturer. The IP address and MAC address are represented in binary in the computer, the IP address is 32 bits, and the MAC address is 48 bits. The length of the MAC address is 48 bits (6 bytes), usually expressed as 12 hexadecimal numbers, separated by a colon every 2 hexadecimal numbers, such as: 08:00:20:0A:8C: 6D is a MAC address, where the first 6 hexadecimal numbers 08:00:20 represent the number of the network hardware manufacturer, which is assigned by the IEEE Institute of Electrical and Electronics Engineers, and the last 3 digits hexadecimal number 0A:8C:6D represents The serial number of a network product (such as a network card) manufactured by the manufacturer. As long as you don't change your MAC address, your MAC address is unique in the world.

0-23 bits are assigned by the manufacturer. 24-47 bits, called organization unique unique (identification of the LAN (local area network) node identifier. The 40th bit is the multicast address flag. The physical address of the network card is usually It is an EPROM (a type of flash memory chip that can be erased by a program) that is burned into the network card by the network card manufacturer. It stores the address of the computer that receives the data and the host that receives the data when transmitting the data.

The image says that the MAC address is like the ID number on our ID card and is globally unique.

Manufacturers of network cards, routers, WIFI wireless products, and Bluetooth products are required to apply for an IEEE OUI code for the product, which is the vendor code of the MAC address. After the manufacturer obtains this code, it adds the 24-bit (bite) manufacturer's own device number to form the MAC address of the device.