How are Virtual Adapter MAC Addresses assigned?

David Kennedy 1 Reputation point
2022-03-07T17:50:23.157+00:00

How are Virtual Adapter MAC Addresses assigned in Windows?

A MAC address is comprised of 6 Octets. The first 3 Octets specify the NIC's (Network Interface Controller) vendor.

We have observed that when a physical NIC exists, a corresponding Virtual Adapter is created. We have also observed that when the corresponding Virtual Adapter is created, the entire Virtual MAC address is the same as the Physical MAC, except that the first Octet is "12" instead of whatever the Physical NIC's first Octet is.

Is this reliable behavior? Will a Virtual MAC that corresponds to a physical NIC always be the Physical MAC's with the first Octet as "12"?

Can we always assume that Virtual MACs start with "12"? Could a Virtual MAC's first 3 Octets ever collide with a real vendor's assigned 3 Octets? (We reviewed the full list of Vendor Prefixes, and the list jumps from 111111: Private to 1402EC: Hewlett Packard Enterprise ~ there are ZERO vendors beginning with "12"). To rephrase, if an observer is looking at the MAC address only, could they infer whether or not a MAC is a virtual NIC or not?

Thank you,

Windows for business | Windows Client for IT Pros | Networking | Network connectivity and file sharing
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  1. Anonymous
    2022-03-16T12:50:01.897+00:00

    Read on here.
    https://learn.microsoft.com/en-us/troubleshoot/windows-server/virtualization/default-limit-256-dynamic-mac-addresses#cause

    --please don't forget to upvote and Accept as answer if the reply is helpful--


  2. Anonymous
    2022-03-17T15:20:32.62+00:00

    Sounds good, you could probably start digging here.
    https://learn.microsoft.com/en-us/windows/win32/nativewifi/about-the-wi-fi-direct-api

    --please don't forget to upvote and Accept as answer if the reply is helpful--

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