What Is a MAC Address?
A MAC (Media Access Control) address is a unique hardware identifier assigned to every network interface card (NIC) at the factory. Unlike IP addresses (which are logical and can change), MAC addresses are burned into the hardware and are intended to be globally unique.
MAC addresses operate at Layer 2 (the Data Link Layer) of the OSI model. They are used to identify devices on a local network segment, enabling Ethernet switches and Wi-Fi access points to deliver frames to the correct device.
MAC Address Format
A MAC address is 48 bits (6 bytes) long, typically written as 6 pairs of hexadecimal digits separated by colons, hyphens, or no separator:
AA:BB:CC:DD:EE:FF (colon notation - most common)
AA-BB-CC-DD-EE-FF (hyphen notation - Windows)
AABBCCDDEEFF (no separator)
AAB.BCC.DDE.EFF (Cisco dot notation)
OUI: The Manufacturer Identifier
The first 3 bytes (24 bits) of a MAC address are the Organizationally Unique Identifier (OUI), assigned by the IEEE to each manufacturer:
AA:BB:CC:DD:EE:FF
└──────┘└──────┘
OUI NIC-specific
(Manufacturer) (Device)
Common OUI examples:
00:50:56- VMware virtual machines00:0C:29- VMware Workstation3C:22:FB- Apple, Inc.00:14:22- Dell Inc.DC:A6:32- Raspberry Pi Trading Ltd.00:1A:2B- Cisco Systems
Special MAC Addresses
| Address | Meaning |
|---|---|
FF:FF:FF:FF:FF:FF |
Broadcast - sent to all devices on segment |
01:00:5E:xx:xx:xx |
IPv4 multicast |
33:33:xx:xx:xx:xx |
IPv6 multicast |
00:00:00:00:00:00 |
Invalid/unset |
The least significant bit of the first byte indicates:
0: Unicast (individual device address)1: Multicast (group address)
The second least significant bit of the first byte indicates:
0: Globally administered (burned in by manufacturer)1: Locally administered (set by software/administrator)
MAC vs IP Address
| Property | MAC Address | IP Address |
|---|---|---|
| Layer | Layer 2 (Data Link) | Layer 3 (Network) |
| Scope | Local network segment | Global or local |
| Uniqueness | Globally unique | Unique within scope |
| Assignment | Hardware (factory) | Software/DHCP |
| Changeability | Technically permanent | Frequently changes |
| Format | 48-bit hex | 32-bit (IPv4) or 128-bit (IPv6) |
MAC Address Spoofing
Despite being "hardware" addresses, MAC addresses can be changed in software (MAC spoofing). This is used legitimately for:
- Network testing and troubleshooting
- Privacy (iOS, Android, Windows randomize MAC per network)
- Bypassing MAC-based access controls for testing
For security purposes, never rely solely on MAC address filtering for network access control.
MAC Randomization for Privacy
Modern devices randomize their MAC address when scanning for networks and can use different MACs per network. iOS 14+, Android 10+, and Windows 10+ all implement this feature by default. The second least significant bit of the first byte is set to 1 for locally administered (randomized) addresses.
Finding Your MAC Address
# Linux
ip link show
# or
ifconfig
# macOS
ifconfig en0 | grep ether
# Windows
ipconfig /all
# Look for "Physical Address"
Using This Tool
Enter any MAC address to look up:
- Manufacturer name from the IEEE OUI database
- Device type (if identifiable)
- Whether the address is unicast/multicast and globally/locally administered
- Formatted versions in all common notations
-> Try the MAC Address Generator