DHCP Client Experiences Delays During Name Resolution

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

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

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.