For omitting certain devices (by mac address) from DHCP assignment:
server = 8.8.8.8 server = 8.8.4.4 dhcp-host=00:50:56:*:*:*,set:blocked dhcp-mac=set:blocked,00:50:56:*:*:* dhcp-ignore=tag:blocked
Used to prevent VMWare provisoned devices from picking up an address outside their lab.