Microsoft KB Archive/810839

= VPN Client Cannot Establish a Connection After You Install a Service Pack =

Article ID: 810839

Article Last Modified on 2/1/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows XP Tablet PC Edition
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Service Pack 3
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Service Pack 1
 * Microsoft Windows 2000 Service Pack 3
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Service Pack 1

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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit 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 you try to establish a virtual private network (VPN) connection from your Windows XP or Windows 2000 PPTP client to your corporate network, the connection may not work, and you may receive the following error message:

Error 721: Remote PPP peer is not responding



CAUSE
This problem occurs when a Windows XP Service Pack 1 (SP1) or Windows 2000 Service Pack 3 (SP3) PPTP client tries to establish a VPN connection to a Windows 2000 server that participates in a cluster that is using the cluster's virtual IP address on TCP port 1723. When the server responds by using Generic Routing Encapsulation (GRE) packets, it uses the source IP address of the first IP address that is bound on the network adapter. However, this address is different from the virtual IP address that is requested by the Windows XP client. The Windows XP client drops these response packets because they originate from a different source IP address from the address that it tried to connect to.



Service Pack Information
To resolve this problem, obtain the latest service pack for Microsoft Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

Hotfix Information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows 2000 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

  Date         Time   Version        Size    File name ---  03-Dec-2002  11:57  5.0.2195.6150  47,088  Raspptp.sys 13-Nov-2002 15:36  5.3.10.0        4,096  Spmsg.dll 13-Nov-2002 15:37  5.3.10.0       87,040  Spuninst.exe 15-Nov-2001 15:27  n/a             5,149  Empty.cat

Update Folder

Date        Time   Version  Size      File name ---  03-Dec-2002  15:20  n/a         7,409  Q810839.cat 13-Nov-2002 15:37  5.3.10.0   18,432  Spcustom.dll 13-Nov-2002 15:36  5.3.10.0  409,088  Update.exe Note This fix should be applied to your Windows 2000 PPTP server.



WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk. If you want your PPTP client that is running Windows XP SP1 or Windows 2000 SP4 or later to allow connections to a PPTP server that replies by using a different IP address, follow these steps to disable PPTP address validation:  Click Start, and then click Run. In the Open box, type regedit, and then click OK. In Registry Editor, locate the following subkey

where is the network adapter for the WAN Miniport (PPTP) driver. On the Edit menu, point to New, and then click DWORD Value. Type ValidateAddress, and then press ENTER. The default setting for this value is 1 (on); therefore, by setting it to 0, you turn it off.</li> Quit Registry Editor.</li> Restart your computer.</li></ol>

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STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Microsoft Windows 2000 Service Pack 4.

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MORE INFORMATION
For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the article number below to view the article in the Microsoft Knowledge Base:

265173 The Datacenter Program and Windows 2000 Datacenter Server Product

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

271731 Earlier-Version PPTP Clients Cannot Connect to a Windows 2000 Server

Keywords: kbbug kbfix kbwin2000presp4fix kbqfe kbnetwork kbprb kbwin2ksp4fix kbhotfixserver KB810839

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