Stand-alone DHCP servers are not allowed to operate when Active Directory is operating. This is to prevent unauthorized servers operating on the network. A DHCP server initializes and starts providing DHCP services to clients only if the server finds its IP address in the authorized list for each of the enterprise roots reported by other DHCP servers. If it does not find itself in the authorized list for each of the reported enterprise roots, it does not initialize and the DHCP service is stopped.