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Q159822: DHCP Clients’ Ability to Send DHCPDECLINE Message

Article: Q159822
Product(s): Microsoft Windows NT
Version(s): 4.0
Operating System(s): 
Keyword(s): 
Last Modified: 21-FEB-2002

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The information in this article applies to:

- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server version 4.0 
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SUMMARY
=======

In the current implementation of the Microsoft dynamic host configuration
protocol (DHCP) service, if a device is provided with an Internet Provider (IP)
configuration by way of DHCP, we do a courtesy Address Resolution Protocol (ARP)
with the provided IP address. If anyone responds, that means the address is in
use. In this case, when a duplicate IP is detected as the TCP/IP protocol tries
to initialize, a popup message is provided to the user stating that a duplicate
IP address exists. The user is informed to get system administration assistance.
At that point, the TCP/IP protocol initialization is failed and the user can't
access any network resources.

MORE INFORMATION
================

DHCP RFC 1541 permits that instead of informing the user, initiating a manual
process, a DHCP_DECLINE transaction can be returned to the DHCP server. The
server will then allocate a different IP address for the device.

DHCP RFC 1541 indicates that it is the responsibility of the DHCP client to
notify the DHCP server with a DHCP_DECLINE transaction if the client determines
that there is a problem with the DHCP parameters provided by the DHCP Server.

The RFC states:

  3.1 Client-server interaction - allocating a network address:

  The client receives the DHCPACK message with configuration parameters. The
  client performs a final check on the parameters and notes the duration of the
  lease and of the lease identification cookie specified in the DHCPACK
  message. At this point, the client is configured. If the client detects a
  problem with the parameters in the DHCPACK message, the client sends a
  DHCPDECLINE message to the server and restarts the configuration process. The
  client should wait a minimum of ten seconds before restarting the
  configuration process to avoid excessive network traffic in case of looping.

  4.3.3 DHCPDECLINE message:

  If the server receives a DHCPDECLINE message, the client has discovered
  through some other means that the suggested network address is already in
  use. The server MUST mark the network address as "not allocated" and SHOULD
  notify the local system administrator of a possible configuration problem.

The Windows 95/98 Downlevel DHCP Clients have also been updated to include
DHCPDECLINE functionality. Windows 98 includes the DHCPDECLINE ability. For
Windows 95, please refer to either of the following articles:

  ARTICLE-ID: Q191494
  TITLE : Dial-Up Networking 1.3 Upgrade Available

  ARTICLE-ID: Q182108
  TITLE : Availability of Windows Sockets 2.0 for Windows 95

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0. This
problem was corrected in the latest US Service Pack for Windows NT. For
information on obtaining this update, query on the following word in the
Microsoft Knowledge Base (without the spaces):

  S E R V P A C K


Additional query words: w95 SP2

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Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : :4.0
Issue type        : kbprb

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