Microsoft KB Archive/887372

= You cannot connect to a Windows 2000-based virtual private network (VPN) server if one or more of the network routers do not support packet fragmentation =

Article ID: 887372

Article Last Modified on 10/11/2006

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APPLIES TO


 * Microsoft Windows 2000 Professional Edition
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server

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SYMPTOMS
You cannot make virtual private network (VPN) connections to a Microsoft Windows 2000-based VPN server if one or more of the network routers do not support packet fragmentation. In this situation, you find that many packets are dropped if you perform network diagnostics to monitor the network.



CAUSE
The problem occurs because the Maximum Receive Unit (MRU) value in Windows 2000 is hard-coded to 1500 bytes. VPN connections add some extra bytes to the packet headers. This may cause the packet size to exceed the maximum MRU that the router allows. If one or more of the routers do not support packet fragmentation, the packets will be dropped. Therefore, the VPN connection will fail.



RESOLUTION
After you apply this hotfix, the MRU is determined through negotiation with remote computers.

Hotfix information
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 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.

Prerequisites
No prerequisites are required.

Restart requirement
You must restart your 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.



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
For more information about how hotfix packages are named, click the following article number to view the article in the Microsoft Knowledge Base:

816915 New file naming schema for Microsoft Windows software update packages

For more information, 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

Additional query words: pptp, l2tp, rras

Keywords: kbbug kbfix kbhotfixserver kbqfe kbpubtypekc KB887372

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