Cannot Connect to a Windows-Based Server That Is Running NAT If the Client Source Port Is 1723 (817892)


The information in this article applies to:

  • Microsoft Windows Server 2003, Standard Edition
  • Microsoft Windows XP 64-Bit Edition Version 2003
  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows Small Business Server 2003, Premium Edition
  • Microsoft Windows Small Business Server 2003, Standard Edition
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

SUMMARY

If Network Address Translation (NAT) is in use on a server that is running Windows Server 2003 or Windows 2000, connections cannot be made to the server's external interface if the source port of a client computer is port 1723.

You can enable NAT by turning on Internet Connection Sharing or by using Microsoft Internet Security and Acceleration (ISA) Server 2000.

CAUSE

Ipnat.sys does not allow a port that is already associated with the Point-to-Point Tunneling Protocol (PPTP) to be used.

RESOLUTION

Windows Server 2003

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 Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone 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 fix 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
   ----------------------------------------------------
   02-Dec-2003  17:50  5.2.3790.107  80,384  Ipnat.sys
Note As part of the resolution, you must add the following registry entry to the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IpNat\Parameters subkey.

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.

Data type: DWORD
Entry name: DisablePPTPEditor
Value data: 1 (to disable PPTP Editor) or 0 (to enable PPTP Editor)

Set this value to 1 if you are experiencing the problem that is described in this article.

Windows 2000

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone 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 fix 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
   ----------------------------------------------------
   13-May-2003  12:50  5.0.2195.6745  67,184  Ipnat.sys

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
Modification Type:MinorLast Reviewed:10/11/2005
Keywords:kbHotfixServer kbQFE kbQFE kbWinServ2003preSP1fix kbWin2000preSP5fix kbfix kbBug KB817892
©2004 Microsoft Corporation. All rights reserved.