Microsoft KB Archive/251166

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Article ID: 251166

Article Last Modified on 11/1/2006


  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 4.0 Standard Edition

This article was previously published under Q251166


After you apply Windows NT 4.0 Service Pack 5, you may no longer be able to establish NetBIOS connections using an IP address, such as in the following examples:



This issue can occur because Windows NT 4.0 Service Pack 5 does not establish NetBIOS connections like earlier versions of Windows NT.


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



This problem was first corrected in Windows NT 4.0 Service Pack 6.


Before you install Windows NT 4.0 Service Pack 5, Windows NT follows these steps to establish a NetBIOS connection for an IP address:

  1. Establish a TCP session on port 139 (the NetBIOS session port).
  2. Attempt to set up a NetBIOS session using the special "*SMBSERVER" name. If this succeeds, Windows NT proceeds with the NetBIOS session as normal.
  3. If step 2 does not work, a NetBIOS Adapter Status Query is issued to the IP address that was specified. This query occurs on UDP port 137 (the NetBIOS name resolution port). The Adapter Status Query returns a list of all NetBIOS names registered by the target system. This list is parsed for the NetBIOS name registered by the Server Service (<computername>[0x20]).
  4. If step 3 is successful, the TCP session to port 139 is established, and the NetBIOS session is set up using the NetBIOS name found in step 3.

After you apply Windows NT 4.0 Service Pack 5, Windows NT does not perform the first two steps to esablish a NetBIOS connection. However, if step 3 is successful, the connection is established and NetBIOS functions properly.

For security reasons, Network Administrators may want to disable UDP port 137. If this is done, NetBIOS commands that specify an IP address and are initiated from a computer running Windows NT 4.0 Service Pack 5 may not work even though other operating systems or service pack versions may be able to complete the command successfully. For additional information, see the following article or articles in the Microsoft Knowledge Base:

161431 Connecting to NetBIOS Resources Using DNS Names or IP Addresses

Additional query words: SMB

Keywords: kbbug kbfix kbnetwork kbqfe KB251166