Do MAC addresses on virtual machines mean anything?

Question

MAC addresses on virtual installations such as VirtualBox are not connected to hardware.

Do they have any absolute meaning, and are they registered somewhere, the way hardware MAC addresses are supposed to be? Or are they essentially spoofed?

Solution

Essentially they are spoofed.

They can indicate that the unit is a VM but they don't have to. They are generating a MAC address for a virtual adapter so they don't have the opportunity to be "real". How they are generated all depends on the Virtual Machine manufacturer. Here are a few links to how different vendors implement MAC addresses:

• Maintaining and Changing the MAC Address of a Virtual Machine

• Virtual Machine MAC address generation

• VMWare vSphere 4 MAC Address Generation

Comments

[Admin]

Considering I've seen/used [Intel] hardware with randomized MAC addresses (manufacture section constant), I'm not sure I would say they "have any less meaning" ... anyway :) As long as the MAC is "constant" for the duration it needs to be (sometimes a MAC will be used for an UUID ... ICK!), and doesn't cause collisions on the segment, then I'd argue it does its job as much as any.

[Jonathan van de Veen]

The second link in your answer does no longer work. Any chance you can update it?

[IAmTimCorey]

@JonathanvandeVeen - I crossed off the broken link and added a new link. I was not able to recover the broken link's content.