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

Support for Windows XP has ended

Microsoft ended support for Windows XP on April 8, 2014. This change has affected your software updates and security options. Learn what this means for you and how to stay protected.

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.
RESOLUTION

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 available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.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.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
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:
  1. Click Start, and then click Run.
  2. In the Open box, type regedit, and then click OK.
  3. In Registry Editor, locate the following subkey
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\<000x>
    where <000x> is the network adapter for the WAN Miniport (PPTP) driver.
  4. On the Edit menu, point to New, and then click DWORD Value.
  5. 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.
  6. Quit Registry Editor.
  7. Restart your computer.
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.
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
Properties

Article ID: 810839 - Last Review: 02/01/2007 02:48:38 - Revision: 6.8

  • Microsoft Windows XP Home Edition SP1
  • Microsoft Windows XP Professional SP1
  • Microsoft Windows XP Tablet PC Edition
  • Microsoft Windows 2000 Advanced Server SP3
  • Microsoft Windows 2000 Advanced Server SP2
  • Microsoft Windows 2000 Advanced Server SP1
  • Microsoft Windows 2000 Service Pack 3
  • Microsoft Windows 2000 Server SP2
  • Microsoft Windows 2000 Server SP1
  • Microsoft Windows 2000 Service Pack 3
  • Microsoft Windows 2000 Professional SP2
  • Microsoft Windows 2000 Professional SP1
  • kbautohotfix kbhotfixserver kbqfe kbnetwork kbwin2ksp4fix kbwin2000presp4fix kbfix kbbug kbprb KB810839
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