Your DHCP is not authorized?

Most of the time you start your Dynamic Host Configuration Protocol (DHCP) and it returns an error. This issue occurs most of the time with the use of an incorrect IP address for the DHCP server that is being authorized in Active Directory Domain Services. Therefore, Active Directory Domain Services does not recognize the DHCP server when the DHCP server role is installed. It can be very difficult to resolve since Server Manager does not prompt you when Active Directory Domain Services does not recognize the DHCP server.

The first in resolving the issue is to:

1. Click on Start, Administration Tools, then DHCP.
   
2. In the DHCP MMC snap-in, right-click the DHCP server name, and then click Authorize.
   
3. To exit the DHCP MMC snap-in, click Exit on the File menu.
   

This should put you on the right path to resolve the issue. Although, you might need to restart the DHCP Server before the change can take effect. Then click Start, Network, Network and Sharing center, and then make sure the Server and the Network are connected. The go back to Server Manager DHCP services are started. Make sure it sets on automatic. However, you need to make sure you setup statics addresses on the Server and on the Client.

This should let you ping your IP from any Client on the Network.

Reference:
http://support.microsoft.com/kb/954416