MAC Address Generator

Generate random MAC addresses in various formats with bulk output

What is it and how does it work?

A MAC address (Media Access Control address) is a unique 48-bit hardware identifier assigned to a network interface card (NIC). Written as six pairs of hexadecimal digits: `00:1A:2B:3C:4D:5E` (colon-separated), `00-1A-2B-3C-4D-5E` (hyphen-separated), or `001A.2B3C.4D5E` (Cisco dot notation). The first three bytes (OUI — Organizationally Unique Identifier) identify the manufacturer: `00:1A:2B` is registered to a specific company. The last three bytes are assigned by the manufacturer. MAC addresses operate at OSI Layer 2 (Data Link layer) — used for communication within a local network segment, while IP addresses (Layer 3) handle routing between networks.

This tool generates random MAC addresses for testing, network simulation, and development purposes. It supports: unicast/multicast bit control, locally-administered/globally-unique bit control, specific OUI prefix, and multiple output formats. Locally-administered MAC addresses (LAA) have the second-least-significant bit of the first byte set to 1 — these are used for virtual machines, containers, and MAC address spoofing.

Common use cases

• VM network configuration: generate MAC addresses for virtual machine network interfaces — use the LAA bit (locally administered) to ensure they don't conflict with real hardware addresses.
• Network simulation: generate a set of unique MAC addresses to simulate a network of devices in software testing or network protocol development.
• Vendor lookup: generate a MAC address with a known OUI (e.g., `F8:FF:C2` for Apple) to test vendor lookup functionality in network management tools.

Frequently asked questions

What is the OUI (Organizationally Unique Identifier) in a MAC address?

The OUI is the first three bytes (24 bits) of a MAC address, assigned by the IEEE to a specific manufacturer or organisation. For example, `00:50:56` is VMware, `00:0C:29` is also VMware (for VMs), `F8:FF:C2` is Apple. IEEE maintains a public OUI registry. When a device appears on a network, the first three bytes identify who made the NIC (though this can be spoofed). The remaining three bytes are the manufacturer's serial number for that NIC.

What is the difference between a unicast and multicast MAC address?

The least-significant bit of the first byte determines unicast vs multicast. If bit 0 = 0: unicast (intended for a single recipient). If bit 0 = 1: multicast (intended for a group). The broadcast address `FF:FF:FF:FF:FF:FF` has all bits set to 1 (multicast to all). Ethernet switches deliver unicast frames only to the port connected to the destination MAC, but flood multicast/broadcast frames to all ports (or use multicast groups with IGMP snooping).

What is MAC address spoofing?

MAC address spoofing changes a device's MAC address from the factory-assigned value to a different value. Legitimate uses: privacy (randomising MAC to prevent tracking across Wi-Fi networks — iOS, Android, and Windows now do this by default), bypassing MAC-based network filters, testing, and virtual machine networking. Malicious uses: bypassing MAC-based access control lists (ACLs) or impersonating another device. MAC filtering is not a security measure — it's easily bypassed by any attacker who can observe network traffic.

How are MAC addresses used in DHCP?

When a device joins a network and requests an IP via DHCP, the DHCP Discover packet includes the device's MAC address. The DHCP server uses this MAC as a client identifier to: (1) offer an IP address, (2) optionally assign the same IP to the same MAC consistently (DHCP reservation). DHCP leases are tracked by MAC address. Static DHCP mappings (reservations) assign a fixed IP to a specific MAC — useful for servers, printers, and devices that need consistent IPs.

Network

Subnet Calculator · IP Address to Binary · URL Builder · Query String Parser · MIME Type Finder · HTTP Header Builder