MAC Address Generator

Sobre MAC Address

Um endereço MAC tem 48 bits (6 bytes). Os 3 primeiros bytes são o OUI (Organizationally Unique Identifier) atribuído pela IEEE a um fabricante. O bit 1 do primeiro byte indica multicast/unicast e o bit 2 indica se o endereço é local (administered locally) ou universal.

Para endereços de uso interno (VMs, testes, redes locais) prefira definir o bit "locally administered" — o que esta ferramenta faz quando o OUI é aleatório.

How MAC addresses are structured

A MAC address (Media Access Control) is a 48-bit identifier — six bytes written in hexadecimal and separated by colons (00:1A:2B:3C:4D:5E), hyphens (00-1A-2B-3C-4D-5E) or, in Cisco notation, dots grouping 16 bits (001a.2b3c.4d5e). The IEEE 802 standard splits those 48 bits in two halves: the first 24 bits are the OUI (Organizationally Unique Identifier), purchased from the IEEE Registration Authority by hardware vendors, and the last 24 bits — sometimes called the NIC-specific portion — are assigned by the vendor to each card it manufactures.

Well-known OUIs include Apple (00:1A:11), Cisco (00:00:0C), Intel (00:03:47) and VMware (00:50:56). The first byte also carries two control bits: bit 0 (least significant) flags multicast when set to 1 (otherwise unicast) and bit 1 flags locally administered when set to 1 (otherwise globally unique). A Locally Administered Address (LAA) is the IEEE-sanctioned way to use a MAC that is not tied to any registered manufacturer — exactly the convention modern operating systems follow when they randomize the WiFi MAC for privacy (Apple iOS, Android and Windows have shipped MAC randomization since 2014).

Special addresses

The broadcast MAC is FF:FF:FF:FF:FF:FF — a frame addressed to it is delivered to every host on the link. Multicast MACs starting with 01:00:5E map IPv4 multicast groups, while 33:33:xx:xx:xx:xx is reserved for IPv6 Neighbor Discovery and multicast. The EUI-64 transform — used by IPv6 SLAAC to derive an interface ID from a MAC — flips the locally-administered bit and inserts FF:FE in the middle of the 48-bit address to extend it to 64 bits.

MAC spoofing and tooling

Changing a MAC at the OS level is trivial: ip link set dev eth0 address 02:11:22:33:44:55 on Linux, ifconfig en0 ether ... on macOS, or registry edits on Windows. Doing so on your own network is legal and useful for DHCP testing, captive-portal bypass on quotas you paid for or evading device fingerprinting. Doing so on networks you don't own to impersonate someone else's device can violate computer-misuse laws — most jurisdictions treat it as unauthorized access.

FAQ

Does the generated MAC correspond to a real manufacturer? Only if you pick one of the vendor OUIs (VMware, VirtualBox, Apple…). When the OUI is "random", the tool sets the locally-administered bit so the address is, by IEEE convention, not bound to any registered vendor.

Can I use it to register a virtual machine in DHCP? Yes — DHCP only needs the address to be syntactically valid and unique on the link. The output works for KVM, VirtualBox, VMware, Docker macvlan, network emulation and lab setups.

Is a generated MAC globally unique? The OUI block guarantees uniqueness for compliant vendors, but cheap chipsets — especially counterfeit USB-Ethernet and WiFi dongles — have been caught shipping with duplicated MACs. Locally administered addresses are intentionally unique only within your link.

Are MAC addresses sent anywhere? No. Generation runs entirely in your browser; no traffic is sent to the server.