PMTU Detection May Not Work After You Install Windows 2000 Service Pack 2 (301337)

SYMPTOMS

After you install Windows 2000 Service Pack 2 (SP2) on one of your servers, clients may not be able to use that server for different programs, such as Terminal Services, File and Printer sharing, or Microsoft Exchange Server.

Client computers that experience these problems are typically running Microsoft Windows 95, Microsoft Windows 98 or Microsoft Windows Millennium Edition (Me) and are connecting to your network by using Virtual Private Networking (VPN), but may also include Windows 2000 or Microsoft Windows NT 4.0 clients depending upon your network configuration.

If you are using non-Microsoft VPN servers or any routers that are using Network Address Translation (NAT), you may also see these symptoms from client computers.

Your Windows 98 client may receive the following error message when you try to copy files to or from a file share on the remote Windows 2000 server:

Cannot copy file name the specified network resource or device is no longer available.

CAUSE

Windows 2000 SP2 included a change that required computers on the same subnet to use the same MTU, as defined in RFC 1191. After you install Windows 2000 SP2, your server ignores any ICMP destination unreachable messages that instruct it to lower the MTU, if the request to lower the MTU comes from a computer that is on the same subnet.

If your VPN server is assigning IP addresses that are part of the local network, the VPN client and the file server on the LAN are on the same subnet. If your VPN server is not assigning IP addresses that are part of the local network, the computers are not on the same subnet, and this problem does not occur. This problem can also occur if you have clients that are behind a NAT router and servers on the other side of the router that use different MTUs.

RESOLUTION

To resolve this problem, obtain the latest service pack for 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

The following file is available for download from the Microsoft Download Center:

Download Q301337_W2k_SP3_x86_en.exe now

Release Date: January 14, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file. The English version of this fix should have the following file attributes or later:

   Date       Time      Version        Size     File name
   ---------------------------------------------------------
   26-Sep-01  20:11:42  5.0.2195.3951  121,936  Afd.sys
   11-Oct-01  15:07:12  5.0.2195.3952  106,256  Msafd.dll
   27-Sep-01  13:06:14  5.0.2195.4429  312,688  Tcpip.sys
   30-Jul-01  20:15:14  5.0.2195.3988   16,240  Tdi.sys
   11-Oct-01  15:07:12  5.0.2195.3649   17,680  Wshtcpip.dll

NOTE: This hotfix needs to be installed on all Windows 2000 SP2 computers that are exhibiting the symptoms listed above. It is not necessary to put this hotfix on the Windows 2000 VPN server because it already uses an MTU that matches the VPN clients.

PMTU Detection May Not Work After You Install Windows 2000 Service Pack 2 (301337)

SYMPTOMS

CAUSE

RESOLUTION

STATUS