A logon window appears in Windows Server 2003 Service Pack 1 NLB when you try to browse the "virtual NLB cluster name" (914060)


The information in this article applies to:

  • Microsoft Windows Server 2003, Standard Edition
  • Microsoft Windows Server 2003, Enterprise Edition
  • Microsoft Windows Server 2003, Standard x64 Edition
  • Microsoft Windows Server 2003, Enterprise x64 Edition
  • Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
  • Microsoft Windows Server 2003 SP1
Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry

SYMPTOMS

When the following conditions are true, you may receive a logon window that prompts you for credentials:
  • You try to browse the virtual Network Load Balancing (NLB) cluster name.
  • You use a server that is a member of the NLB cluster.
  • The NLB cluster is running Microsoft Windows Server 2003 Service Pack 1 (SP1).
After you type the appropriate credentials, you can view and access all shares. Additionally, you can browse the virtual NLB cluster name from any other client in the network without any problem.

CAUSE

This problem occurs because Windows Server 2003 SP1 includes a security feature that removes the last available authentication mechanism in NLB Manager. This security feature is an authentication loopback check that is designed to prevent man-in-the-middle (MITM) attacks on NTLM.

WORKAROUND

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To work around this problem, use one of the following methods.

Method 1: Create the Local Security Authority host names that can be referenced in an NTLM authentication request

To do this, follow these steps for all the nodes:
  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate the following key in the registry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0

  3. Right-click MSV1_0, point to New, and then click Multi-String Value.
  4. Type BackConnectionHostNames, and then press ENTER.
  5. Right-click BackConnectionHostNames, and then click Modify.
  6. In the Value data box, type the host name that is used for the NLB cluster, and then click OK.
  7. Close Registry Editor, and then restart the computer.

Method 2: Disable the authentication loopback check

To do this, follow these steps for all the nodes:
  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate the following key in the registry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

  3. Right-click Lsa, point to New, and then click DWORD Value.
  4. Type DisableLoopbackCheck, and then press ENTER.
  5. Right-click DisableLoopbackCheck, and then click Modify.
  6. In the Value data box, type 1, and then click OK.
  7. Close Registry Editor, and then restart the computer.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Modification Type:MajorLast Reviewed:3/16/2006
Keywords:kbtshoot kbprb KB914060 kbAudITPRO
©2004 Microsoft Corporation. All rights reserved.