DHCP Client May Fail with WinNT 4.0 SP2 Multinetted DHCP Server (163055)

SYMPTOMS

A DHCP client may fail to obtain a DHCP lease if multiple logical subnets exist and there is a Windows NT 4.0 Service Pack 2 (SP2) DHCP server on the network. Also, you may receive the following error message when you run the IPCONFIG /RENEW command:

Access Denied - Renewing Adapter "xxxx"

Prior to Service Pack 2, when multiple logical subnets existed, the DHCP client was able to receive the DHCPOFFER and send a DHCPREQUEST to the offering DHCP server. After applying Service Pack 2, the DHCP servers on other logical subnets issue a DHCPNACK, which forces the client to release the address and perform a DHCPDISCOVER again.

In addition to the above error message, you may receive the following event log messages:

On the Client

   Event ID: 1006
   Source: Dhcp
   Type: Warning
   Category: None
   Description: DHCP service is shutting down. The following error
                occurred: Access is denied.

On the Server

   Event ID: 1011
   Source: DhcpServer
   Type: Warning
   Category: None
   Description: The DHCP server issued a NACK to the client (MAC Address of
                the Requesting Client) for the address (Requested IP
                Address) request.

CAUSE

Windows NT 4.0 SP2 DHCP servers issue a DHCPNACK to any DHCPREQUEST that does not appear to be valid for the subnet. This problem occurs when you are using multiple logical IP subnets (multinetting) and two DHCP servers on the same physical network are serving two different logical subnets.

For example, a client broadcasts DHCPREQUEST and receives ACK from server A and NACK from server B. Because there is no communication between server B and server A, server B is not aware of the existence of server A. If it does not send a NACK, then a client who has just moved to this network will never know that its old address is invalid.

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack

To workaround this issue, use one of the following:

Windows NT 4.0 SP2 includes the ability to create DHCP superscopes. After creating a scope and defining each logical subnet in a superscope, the DHCP server recognizes the DHCPREQUEST as valid and will not NACK the request.

For example, you have a multinet environment with the following DHCP servers on a single LAN:
192.168.10.1
192.168.20.1
192.168.30.1
On each DHCP server you must create a superscope with a minimum of one IP address from each of the 10.x, 20.x and 30.x scopes. Be sure not to duplicate IP addresses in the scopes.

-or-
Another possibility is to take advantage of the superscoping feature and create one DHCP server to serve all scopes.

For more information on superscopes, please see the following article in the Microsoft Knowledge Base:

ARTICLE-ID: 161571
TITLE : Using DHCP "Superscopes" to Serve Multiple Logical Subnets