SEPM 12 RU3 - Filter Unmanaged Detector Based on Range of Mac addresses

In our SEPM 12 RU3 environment, the Unmanaged Detector is showing printers, routers, scanners, etc as not having SEP client installed.

I understand you can add Unmanaged Detector Exceptions based on a range of IP addresses, but how do I create exception based on a range of Mac addresses. Or the first three octets of Mac address.

I am unable to type in wildcard in the last three octets, i.e. 00 - 04 - 00 - * - * - *

and when I leave las three octets blank I get an error from SEPM, "The MAC address is not a valid address"

How to get around this? I want to avoid using range of IP addresses because they change easily.