Understanding 48-Bit MAC Addresses & IEEE OUIs
A Media Access Control (MAC) address is a unique 48-bit (6-octet) physical hardware identifier embedded onto Network Interface Cards (NICs), Wi-Fi radios, and Ethernet controllers. Under IEEE 802 specifications, the address is divided into two 24-bit segments:
- Organizationally Unique Identifier (OUI): The first 3 octets (e.g.
BC:D0:74) are assigned by the IEEE Registration Authority to hardware vendors (such as Apple, Cisco, or Intel).
- Network Interface Controller (NIC) Specific: The last 3 octets (e.g.
2A:8B:11) are assigned by the manufacturer to identify individual device units.
What is Private MAC Address Randomization?
Modern mobile operating systems (iOS 14+, Android 10+, Windows 11) use MAC Randomization to prevent commercial Wi-Fi hotspots and retail tracking beacons from logging your physical movements across locations. When enabled, your phone generates an ephemeral, pseudo-random MAC address for each Wi-Fi network.
You can identify a randomized MAC address by examining the second hexadecimal digit of the first octet. If it is 2, 6, A, or E (e.g., DA:A1:19...), the Locally Administered (U/L) bit is set to 1, indicating a randomized private address rather than a factory-burned OUI.
How to Find Your Device's Physical MAC Address
| Operating System |
Terminal / Command Prompt Method |
Settings GUI Navigation |
| Windows 11 / 10 |
getmac /v or ipconfig /all |
Settings > Network & internet > Wi-Fi > Hardware properties |
| macOS (Apple Silicon/Intel) |
networksetup -getmacaddress "Wi-Fi" |
System Settings > Network > Wi-Fi > Details > Hardware |
| iPhone / iPad |
N/A |
Settings > General > About > Wi-Fi Address |
| Android |
N/A |
Settings > About Phone > Status Information > Wi-Fi MAC address |
Media Access Control (MAC) Architecture & IEEE OUI Registry Guide
In the OSI (Open Systems Interconnection) reference model, a Media Access Control (MAC) address functions as the unique physical hardware identifier at the Data Link Layer (Layer 2). Bound directly to Network Interface Cards (NICs), Ethernet controllers, and WiFi radios, MAC addresses govern local frame transmission across local broadcast domains.
1. Structural Anatomy of a 48-bit MAC Address (EUI-48)
A standard MAC address comprises 48 bits (6 octets), conventionally represented as six pairs of hexadecimal digits separated by colons or hyphens (e.g., 00:1A:2B:3C:4D:5E):
- Organizationally Unique Identifier (OUI - First 24 Bits): Assigned by the Institute of Electrical and Electronics Engineers (IEEE) Registration Authority to identify hardware manufacturers (such as Apple, Cisco, Intel, Samsung, or Raspberry Pi).
- Network Interface Specific Identifier (Last 24 Bits): Assigned by the individual hardware manufacturer as a unique serial number for the physical network interface.
2. The Unicast/Multicast (I/G) and Universally/Locally Administered (U/L) Bits
The first transmitted octet contains two critical binary control flags located in its least significant bits:
- Bit 0 (I/G - Individual/Group): If set to
0, the frame is Unicast (destined for a single host). If set to 1, the frame is Multicast or Broadcast (e.g., FF:FF:FF:FF:FF:FF).
- Bit 1 (U/L - Universal/Local): If set to
0, the MAC address is Universally Administered (officially assigned by the IEEE and vendor). If set to 1, the address is Locally Administered (manually assigned or randomized by software).
3. Modern MAC Address Randomization in Mobile Operating Systems
Because physical MAC addresses historically remained static, commercial retail tracking systems deployed passive WiFi sniffing beacons to track foot traffic and consumer movement across retail spaces. In response, modern operating systems (iOS 14+, Android 10+, Windows 11) now implement automated MAC address randomization by default, generating unique locally administered MAC addresses for each separate SSID to safeguard subscriber privacy.