MAC Address Generator

A MAC (Media Access Control) address is the 48-bit hardware identifier burned into every Ethernet, Wi-Fi, and Bluetooth network interface. It is written as 12 hex digits in pairs (AA:BB:CC:DD:EE:FF) and is what your switch, router, or access point uses to deliver frames on the local link. Unlike an IP address, which can change every time you join a different network, a MAC address travels with the physical NIC.

The first 24 bits (3 bytes) of a MAC are the Organizationally Unique Identifier, a block of address space the IEEE Registration Authority assigns to one hardware vendor. F4:F5:DB belongs to Apple, 00:1A:2B to Cisco Systems, 00:50:56 to VMware, and so on. Vendors then assign the remaining 24 bits to each NIC they ship. Setting the vendor prefix box in the generator pins the first 3 bytes to a real OUI, which is useful when you need addresses that look like they came from a specific manufacturer in a lab or testbed.

Bit 1 of the first octet (the second-least-significant bit) is the U/L flag: 0 means the address is universally administered (IEEE-assigned to a real vendor) and 1 means it is locally administered (made up). By default this generator sets that bit on random addresses, so they look like 02:xx:xx, 06:xx:xx, 0A:xx:xx, or 0E:xx:xx and are guaranteed not to collide with any real OUI. The same convention is what your hypervisor uses when it auto-generates MACs for virtual machines.

Colon notation (AA:BB:CC:DD:EE:FF) is the Linux, macOS, and Unix default and is what most network tools accept. Hyphen notation (AA-BB-CC-DD-EE-FF) is the Windows ipconfig and IEEE 802 default. Cisco dot notation (AABB.CCDD.EEFF) groups the 12 hex digits into three 4-character blocks and is the format every Cisco IOS, NX-OS, and IOS XR command uses. Raw (AABBCCDDEEFF) is handy when you need to paste the address into config files or scripts that expect no separators.

Common uses are provisioning unique MACs for virtual machines and containers (most hypervisors will auto-assign one from the 02:00:00 range, but you sometimes need to pin a value), populating DHCP reservation tables in a lab, generating fixture data for automated network tests, seeding MAC spoofing on a workstation, and simulating large numbers of clients for load testing. Modern phones and laptops also randomize their Wi-Fi MAC per network (iOS Private Wi-Fi Address, Android MAC Randomization) using exactly the same locally administered bit trick.