If a DHCP server is to operate within an Active Directory domain (and is not running on a domain controller) it must first be authorized.
This can be achieved either as part of the DHCP Server role installation, or subsequently using either DHCP console or at the command prompt using the netsh tool.
If the DHCP server was not authorized during installation, invoke the DHCP console (Start - All Programs - Administrative Tools - DHCP),
right click on the DHCP to be authorized and select Authorize. To achieve the same result from the command prompt, enter the following command:
netsh dhcp server serverID initiate auth
In the above command syntax, serverID is replaced by the IP address or full UNC name of system on which the DHCP server is installed.