How to use the mac address generator
- Set the count to choose how many addresses you need, from 1 to 50.
- Pick a format: colon-separated, hyphen-separated, Cisco dot notation or plain hex.
- Select uppercase or lowercase for the hex digits.
- Optionally enter a 6-digit OUI prefix to fix the first three octets, or choose an address type to set the standard bits automatically.
- Click Generate to produce your list of random MAC addresses.
How MAC address bits work
A MAC address is six bytes long. The first byte contains two special bits defined by IEEE 802. Bit 0 (the least significant bit) is the Individual/Group bit: 0 means unicast, 1 means multicast. Bit 1 is the Universal/Local bit: 0 means universally administered (assigned by the manufacturer), 1 means locally administered.
This mac address generator lets you control those bits through the Address type field. Choosing Universal unicast clears both bits so that first_octet & 0x03 == 0x00. Choosing Locally administered sets bit 1 and clears bit 0 so that first_octet & 0x03 == 0x02. When you supply an OUI prefix, the tool applies the bit mask on top of your prefix bytes.
Format reference table
Different operating systems and network equipment expect different notations. Here is how the same six bytes appear in each format this tool supports:
| Format | Example | Common use |
|---|---|---|
| Colon | 00:1A:2B:3C:4D:5E | Linux, macOS, general networking |
| Hyphen | 00-1A-2B-3C-4D-5E | Windows ipconfig output |
| Cisco dot | 001A.2B3C.4D5E | Cisco IOS and NX-OS |
| None | 001A2B3C4D5E | Databases, APIs, raw storage |
The random mac address generator outputs whichever format you select so you can paste directly into configuration files or test scripts without manual reformatting.
Using an OUI prefix
An Organizationally Unique Identifier (OUI) is the first three octets of a MAC address, assigned by IEEE to a specific vendor. For example, 00:16:3E belongs to XenSource. By entering 00163E in the OUI field, every generated fake mac address will start with those three bytes while the remaining three are filled with cryptographically random values.
This is useful when you need addresses that look like they belong to a particular vendor during integration testing or lab setups. The OUI must be exactly six hexadecimal characters. If you also select an address type, the tool adjusts the first octet's lower two bits after applying your OUI.
Practical use cases
Developers and network engineers use a mac address generator online for several tasks:
- Virtual machine testing: Assign unique locally administered addresses to VMs or containers to avoid conflicts on a shared bridge.
- Network simulation: Populate topology tools with realistic-looking addresses when modelling large networks.
- Privacy research: Study MAC randomisation behaviour by generating batches of addresses with specific bit patterns.
- Database seeding: Fill development databases with valid-format identifiers without using real hardware addresses.
For other kinds of test identifiers, you might also use the UUID generator or the IMEI generator.
Common mistakes to avoid
When working with fake mac address values, keep these pitfalls in mind:
- Multicast bit set unintentionally: If bit 0 of the first octet is 1, the address is multicast. Most host configurations reject multicast source addresses. Use the universal-unicast or locally-administered type to prevent this.
- Wrong separator: Pasting colon-formatted addresses into a Cisco device expecting dot notation causes parse errors. Always match the target system's expected format.
- OUI length: Entering fewer or more than six hex digits for the OUI will be rejected. Do not include separators in the OUI field.
- Reusing addresses: In large test environments, collisions become likely if you generate too few addresses. Request enough unique values up front.
Worked examples
| Example | Input | Result |
|---|---|---|
| Five colon-separated uppercase | Count: 5; Format: colon; Case: upper; Address type: any | D4:ED:E4:35:DE:16, C9:71:9F:37:4A:6B, AA:8B:AB:1B:6F:65, B1:28:00:F7:AA:FB, 3E:67:F2:3E:52:6E |
| Locally administered, lowercase | Count: 3; Format: hyphen; Case: lower; Address type: locally-administered | 76-06-59-fd-65-8b, 7e-3e-43-71-cb-c5, da-e9-ba-e9-fa-8b |
| Xen OUI prefix, Cisco format | Count: 4; Format: cisco; Case: upper; Address type: any; OUI prefix (optional): 00163E | 0016.3EF9.BF32, 0016.3E52.4946, 0016.3EC2.E403, 0016.3E0D.33CA |
| Universal unicast, plain hex | Count: 2; Format: none; Case: lower; Address type: universal-unicast | 74866db25f18, d05ecb7cce71 |
FAQ
Is this mac address generator safe to use?
Yes. All generation happens locally in your browser using the Web Crypto API. No addresses are sent to any server.
What does locally administered mean?
It means bit 1 of the first octet is set to 1, indicating the address was assigned by a local administrator rather than burned in by the hardware manufacturer.
Can I use these addresses on a real network?
You can use locally administered addresses for testing on isolated networks. Using them on production networks may conflict with existing devices if you do not verify uniqueness first.
Why would I set an OUI prefix?
Setting an OUI makes the generated addresses appear as though they belong to a specific vendor, which is helpful when testing software that filters or routes traffic based on vendor prefixes.
What is Cisco dot notation?
Cisco dot notation groups the twelve hex digits into three blocks of four separated by periods, such as 001A.2B3C.4D5E. It is the default display format on Cisco IOS devices.
How are the random bytes produced?
The tool uses crypto.getRandomValues to fill all six bytes with cryptographically secure randomness, or keeps the first three bytes from your OUI and randomizes the last three. The first byte then has its two low bits set according to the address type, which defaults to universal unicast.