By default MAC addresses are automatically created using random numbers. Oracle VM Manager chooses a MAC address using random numbers within the specified range when the user doesn't supply a specific MAC address. The default range has an OUI (Organizationally Unique Identifier), of 00:21:F6 and uses the remaining portion of 00:00:00 - FF:FF:FF from which to randomly choose a specific MAC address. This default range is used because the OUI prefix (00:21:f6) is officially registered to Oracle and should not conflict with any other vendors devices. However, that range can be changed.
You have the ability to manually configure specific MAC addresses. When a vnic is created, the user can specify any MAC address. The user supplied MAC address does not have to fall within the default range. The manager will validate that this MAC address is not already used by another vnic created in that manager.
You can program your own Organizationally Unique Identifier(OUI). The manager allows the specification of an OUI other than the default and a range of addresses to use for the device specific portion of the MAC address.
You can set the range based allocation of MAC for each Oracle VM Manager instance to avoid collision. The users need to explicitly set the range that they want to use. With coordination among Oracle VM Manager instances, you can set the range so that each Oracle VM Manager won't conflict with other Oracle VM Manager instances.