Windows NT 4.0 ServiceProvider Priority Values Not Applied

Last reviewed: February 10, 1998
Article ID: Q171567
The information in this article applies to:
  • Microsoft Windows NT Workstation version 4.0
  • Microsoft Windows NT Server version 4.0

SYMPTOMS

You may notice that changing the ServiceProvider priority values, as specified in Knowledge Base article Q139270, "How to Change Name Resolution Order on Windows 95 and Windows NT," does not change the hostname resolution order as expected.

CAUSE

Unlike Windows NT 3.x, Windows NT 4.0 does not implement the ServiceProvider priority values.

RESOLUTION

Contact Microsoft Technical Support to obtain the updated files mentioned below.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

MORE INFORMATION

In the fix mentioned above, Microsoft has added a new registry value to the TCP/IP service that allows an administrator the option of changing the hostname resolution order. By default, hostname resolution is performed by Domain Name Service (DNS) first, followed by NetBIOS over TCP/IP (NetBT), if DNS fails. With the use of this registry value, the order of hostname resolution can be reversed.

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.

To change the hostname resolution order (between DNS and NetBT name resolution mechanisms), perform the following steps:

  1. Run Registry Editor (Regedt32.exe).

  2. Go to the following key in the registry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

  3. On the Edit menu, click Add Value and enter the following value information:

          Value Name: DnsNbtLookupOrder
          Data Type:  REG_DWORD
    
          Value:      1 or 0 (default=0, value of 1 causes NetBT name
                      resolution to be attempted before DNS)
    
    

  4. Exit the Registry Editor and restart the computer for the change to take effect.

Using NetBT for name resolution can provide an additional benefit in multi-homed environments. When there is more than one IP address available for a network device, normally a DNS Server will return the list of addresses in a "round robin" fashion, rotating the list with each response to provide load balancing. Windows Sockets applications receive the list of IP addresses ordered as they were provided by the DNS server, and normally attempt to connect to the first address in the list. If these addresses are on different subnetworks, then the application may attempt to connect to the server using an address that is not on the local subnet even though one is available.

WINS returns the list in the same order every time. NetBT uses the local route table to sort the IP addresses in the list into the "best" order. In the case where the calling system shares a common subnet with the called system, the "best" IP address would be the one on the same subnet, and this would be used every time. Because of this sorting, using NetBT name resolution can result in performance and efficiency improvements.


Additional query words: 4.00 multihomed
Keywords : kbbug4.00 kbfix4.00 ntregistry NTSrvWkst nttcp kbnetwork kbnetwork
Version : 4.0
Platform : winnt
Issue type : kbbug
Solution Type : kbfix


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Last reviewed: February 10, 1998
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