You must be logged on as an administrator or belong to the Administrators group to complete these steps.
To authorize a DHCP server in Active Directory Domain Services:
At the DHCP server computer, click Start, point to Administrative Tools, and then click DHCP.
In the console tree, click DHCP.
On the Action menu, click Manage authorized servers.
The Manage Authorized Servers dialog box appears. Click Authorize.
When prompted, type the name or IP address of the DHCP server to be authorized, and then click OK.