MAC addresses are used to restrict packet transmission to the intended recipient. MAC addresses are generated for virtual network adapters that virtual machines and network services use. You can also assign static MAC addresses.

Each virtual network adapter in a virtual machine is assigned its own unique MAC address. Each network adapter manufacturer is assigned a unique three-byte prefix called an Organizationally Unique Identifier (OUI), which it can use to generate unique MAC addresses.

VMware has the following OUIs:

Generated MAC addresses

Manually set MAC addresses

For legacy virtual machines, but no longer used with ESXi