DOCUMENT:Q169838  09-AUG-2001  [winnt]
TITLE   :DHCP Client Experiences Delays During Name Resolution
PRODUCT :Microsoft Windows NT
PROD/VER:WinNT:4.0
OPER/SYS:
KEYWORDS:kbnetwork

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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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SYMPTOMS
========

When a dynamic host configuration protocol (DHCP) client is moved from a subnet
where a Domain Name Service (DNS) server is configured through DHCP, to a subnet
where no DNS server is used or available, delays may occur when names are being
resolved. This can result in slow startup of applications such as Microsoft
Outlook or Microsoft Exchange, or Web browsers.

CAUSE
=====

If a network client obtains a DHCP lease from one server and then releases that
lease, two registry values are not cleaned up:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TCPIP
     \Parameters\DhcpNameServer

-and-

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TCPIP
     \Parameters\DhcpDomain

The Microsoft DHCP client software does not properly remove these values when a
lease is released.

WORKAROUND
==========

To work around this problem, perform one of the following:

 - Configure the DHCP scope for the subnet that the client is moving to, to
   assign a DNS server if one is available.

   -or-

 - Use Registry Editor to clear these values after the client is moved to the
   new subnet.

   If you expect to change frequently between DNS and non-DNS enabled
   environments, you can use a registry file to easily disable the DNS entries
   in the registry. To do this, perform the following steps:


WARNING: Using Registry Editor incorrectly can cause serious, system- wide
problems that may require you to reinstall Windows NT to correct them. Microsoft
cannot guarantee that any problems resulting from the use of Registry Editor can
be solved. Use this tool at your own risk.

   1. Use a text editor (such as Notepad) to create the following file and name
      it Disabledns.reg:

      REGEDIT4

      ; Disable DNS entries in the registry.
      ; There are 2 entries for this key, NameServer and DHCPNameServer
      ; DHCPNameServer is written by the DHCP client service, if enabled.
      ; But if the NameServer parameter has a valid value, it will
      ; override the DHCPNameServer parameter.

      [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
         \Tcpip\Parameters]
         ; "NameServer"=""
         "DhcpNameServer"=""

   2. Save Disabledns.reg to your desktop, or create a shortcut to this file on
      your desktop.

      Running this file clears the DhcpNameServer registry entry. After you are
      connected to the network, renewing the IP address from the DHCP server
      recreates the correct entries in the registry and lets you use the name
      server again.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0. We are
researching this problem and will post new information here in the Microsoft
Knowledge Base as it becomes available.

Additional query words: delay name resolution ipconfig /release
======================================================================
Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : WinNT:4.0
Hardware          : ALPHA PPC x86
Issue type        : kbbug

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