There are two types of addresses:
Those assigned to bridged adapters have the following format: 00-18-51-XX-XX-XX
- Routed adapters' MAC addresses are generated as 00-FF-XX-XX-XX-XX.
In both cases, XX-XX-XX-XX and XX-XX-XX are the first 4 or 3 bytes of the container GUID.
A user can set the MAC address manually as well.
There is the possibility of address conflicts, as XX-XX-XX are random values. There is no collision prevention mechanism implemented at the present moment.