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MAC Address Generator

MAC Address Generator is part of Toolspire and is ready as soon as this page loads. The low bit of the first octet says multicast. The next bit says the address was chosen locally rather than burned in by a vendor. Generated addresses set the local bit and clear the multicast bit.

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What you can do here

Read the two bits that matter

The detail says unicast or multicast, and local or universal. The other bytes are not turned into a manufacturer name.

One canonical spelling

Whatever separators you paste, the headline is lowercase hex with colons.

A lab address, not a disguise

The button builds a local unicast address for a virtual machine or a lab you are allowed to configure. It is not a way onto someone else’s network.

The sequence

How to use the MAC Address Generator

  1. 1

    Paste an address to read it

    Colons, dashes or Cisco dots are fine. You need 12 hex digits. Anything else is refused.

  2. 2

    Read local versus universal

    A burned-in adapter address has the local bit clear. An address a hypervisor invented usually has it set.

  3. 3

    Generate only for a machine you may configure

    Press the button, then use the result in a lab or a VM setting you control. Do not put it on a network where you are not allowed to choose the address.

Worth knowing

  • MAC Address Generator on Toolspire: A MAC is 48 bits, shown as six hex bytes. Colons, dashes and Cisco groups of four (001A.2B3C.4D5E) all parse.
  • The lowest bit of the first byte is the group bit. 1 means multicast or broadcast. 0 means unicast.
  • The next bit is the local bit. 1 means locally administered. 0 means a universally administered, vendor-style address.
  • Generate sets those bits to local and unicast (xxxxxx10 in the low two bits). It does not copy a real vendor prefix, and it does not look one up.

Why the generated address is locally administered

The IEEE leaves a bit so that software can mint an address without colliding with a factory prefix. That is the local bit, the second-lowest bit of the first octet. This generator sets it and clears the group bit, so the result is a unicast address that does not pretend to be a particular vendor’s hardware. There is no manufacturer database on the page, because a partial list would mis-name most addresses. Use the result where you are allowed to set a virtual adapter. It is not a tool for slipping past an access list on a network you do not administer.

FAQ

Questions about MAC Address Generator

Where does MAC Address Generator run?

MAC Address Generator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What does locally administered mean?

The address was chosen by software or by an administrator, not burned into a card by a manufacturer. The second-lowest bit of the first octet is 1.

What is the multicast bit?

The lowest bit of the first octet. When it is 1, the address names a group, not a single adapter. ff:ff:ff:ff:ff:ff is the broadcast address and that bit is set.

Will this tell me the vendor?

No. The other five bytes are not looked up. A vendor guess from a short table would be wrong too often to print.

Can I use a generated address on any network?

Only on a lab or a virtual machine you are allowed to configure. The page will not help you substitute an address to get past someone else’s filter.

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