Fake MAC address generator — locally administered, never a vendor's

How to use the fake MAC address generator

1. Pick a Format: Colon (02:1a:…), Dash (02-1A-…), Cisco dot (021a.2b3c.4d5e) or No separator.
2. Tick Uppercase if your system shows MACs in capitals. Lowercase is the default.
3. Set How many addresses (up to 1,000) and press Generate.
4. Copy the list.

What it does and when to use it

MAC addresses identify network interfaces on a local network. You need made-up ones when you configure virtual machines or containers, write DHCP reservations and switch configs for a lab, fill sample logs and inventory sheets, or test software that parses network data.

A truly random 48-bit value is not a good choice. It may copy a real vendor’s prefix, or it may have the multicast bit set, which makes it invalid for a single device. This tool fixes both bits, so every address is a proper unicast address in the space reserved for local use.

The format menu covers the usual spellings: colons for Linux and macOS, dashes for Windows, and dotted groups of four for Cisco switches. For IP addresses to go with your MACs, use the fake IP address generator. For raw random bytes, the random hex generator is simpler. For a complete sample dataset, see the bulk fake data generator.

How it works

The tool takes 6 random bytes from crypto.getRandomValues. In the first byte it clears the lowest bit (the multicast flag, so the address is unicast) and sets the next bit (the local flag). The first byte therefore always ends in binary 10, which in hex makes the second digit 2, 6, A or E. The other 46 bits stay random. The bytes are then written in the chosen format and case.

Worked examples

Sample output; your addresses will differ.

• Colon, lowercase: e6:8f:00:dc:ea:3b and 72:ad:af:76:aa:d0. The second digits are 6 and 2.
• Cisco dot, uppercase: FED8.6CE5.2780 and 8620.8AE9.44EC. Here the second digits are E and 6.

Under every list the tool adds the note that each address “is unicast with the locally administered bit set (second hex digit 2, 6, A or E)”.

Limits and tips

• The tool cannot make factory-style addresses with a real vendor prefix. That is deliberate.
• Some old or strict systems reject locally administered addresses. Test with the target system first.
• In a lab, keep a list of the MACs you assign, because random values are hard to remember when you read logs later.