Microsoft KB Archive/935945

= The packets that are sent to the local computer are dropped after you establish a VPN connection by using a third-party VPN adapter on a Windows Vista-based computer =

Article ID: 935945

Article Last Modified on 8/29/2007

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APPLIES TO


 * Windows Vista Ultimate
 * Windows Vista Home Premium
 * Windows Vista Home Basic
 * Windows Vista Enterprise
 * Windows Vista Business
 * Windows Vista Business 64-bit Edition
 * Windows Vista Ultimate 64-bit Edition
 * Windows Vista Home Premium 64-bit Edition
 * Windows Vista Home Basic 64-bit Edition
 * Windows Vista Enterprise 64-bit Edition

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SYMPTOMS
Consider the following scenario. You install a third-party virtual private network (VPN) adapter on a Windows Vista-based computer. Then, you establish a VPN connection by using the VPN adapter. In this scenario, the packets that are sent to the local computer are dropped. Therefore, some applications that use the VPN adapter have communication difficulties. Additionally, when other computers initiate connections, these connections may fail.



CAUSE
An error occurs when Windows Vista and the VPN software configure the local routing table. An incorrect route may prevent identification of the packets as packets whose destination is the local computer. Therefore, the packets are dropped.



Hotfix information
A supported hotfix is now 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 service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or 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. To create a separate service request, visit the following Microsoft Web site:

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

Prerequisites
No prerequisites are required.

Restart requirement
You must restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
The English version of this hotfix has the file attributes (or later file attributes) 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 item in Control Panel.

Windows Vista, 64-bit versions


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
To provide loopback connectivity and to handle incoming packets, the TCP/IP protocol requires a local IP address route. This route has a netmask of 255.255.255.255, and the route points to the local address object. In Windows Vista, this route is configured by the TCP/IP protocol. Other components should not configure the route.

However, when certain VPN adapters are installed, the Routing and Remote Access service may configure the local IP address route to point to an IP address other than the local computer address. Therefore, the TCP/IP protocol cannot configure the route to point to the local address object. In this situation, the local address is not recognized. Therefore, all incoming packets that are sent to the local address are dropped. For more information about the standard terminology that is used to describe Microsoft software updates, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbbug kbfix kbqfe kbpubtypekc kbexpertiseinter kbhotfixserver kbwinvistapostrtmfix KB935945

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