https://support.microsoft.com/en-us/kb/816592
- The DHCP server always registers and updates client information with its configured DNS servers.
This is a modified configuration supported for Windows Server 2003-based DHCP servers and clients that are running Windows Server 2003, Windows 2000, or Windows XP. In this mode, the DHCP server always performs updates of the client's FQDN and leased IP address information regardless of whether the client has requested to perform its own updates.
To configure a DHCP server to register and to update client information with its configured DNS servers, follow these steps:
Open the DHCP properties for the server
Click DNS, click Properties, click to select the Enable DNS dynamic updates according to the settings below check box, and then click Always dynamically update DNS A and PTR records.