Microsoft KB Archive/160990

{| = DHCP Server Offers Duplicate IP Addresses for Windows NT =
 * width="100%"|

Last reviewed: February 4, 1998

Article ID: Q160990 The information in this article applies to:
 * Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS
In network environments that allow duplicate routes between DHCP clients and a DHCP server, a DHCP server gives out one IP address to two different clients. This problem occurs with DHCP Server for Windows NT 3.51 and 4.0.

CAUSE
The cause of this behavior is that, in some cases, the processing of the second Discover packet causes the server to set the address state of the address from leased to offered when the DHCP Server sends the second Offer. The client will not reply to the second Offer, because it already has an active lease. Because the DHCP Server does not receive a Request packet in response to the Offer, the lease on the Offered address will timeout and the address will be placed back into the pool of IP addresses available for lease.

STATUS
Microsoft has confirmed this to be a problem in Windows NT version 3.51 and 4.0. This problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

MORE INFORMATION
This problem may occur in several different network environments, including Token Ring environments with large numbers of source routing bridges (where the bridges would be set up in a way that would provide multiple, unique routes between the server and client) and Ethernet environments with multiple routers enabled with BOOTP relay agents or IP helper addressing.

There was a fix for this behavior included in Service Pack 2 for Windows NT 4.0 and Service Pack 5 for Windows NT 3.51. There are certain circumstances in which the DHCP Server gives out the same IP address to two different clients even though the appropriate service packs, mentioned previously, were applied to the server(s).

Keywords         : kbbug3.51 kbbug4.00 kbfix3.51 kbfix4.00 kbfix4.00.sp3 NTSrvWkst kbnetwork Version          : 3.51 4.0 Platform         : winnt Solution Type    : kbservicepack
 * }