Infoblox is a solution that provides network services such as DNS or DHCP in a simple manner. This combination is ideal since for this purpose it works continuously with the same data that macmon uses for Network Access Control.
Your added value: Using the respective open interfaces it is possible to compare the databases with one another and to ascertain the group membership. A maintenance of system data such as MAC-addresses or IP-addresses has to be proceeded at one place only.
Both Infoblox and macmon have corresponding automatisms that guarantee effectively a permanent and updated overview.