You do not receive ICMP "Destination Unreachable" messages after you install the MS05-019 security update on a Windows XP Service Pack 2-based computer (909278)

SYMPTOMS

Consider the following scenario. You have installed the MS05-019 security update on a Microsoft Windows XP Service Pack 2 (SP2)-based client computer. Microsoft Windows Firewall is enabled on the client computer. When you try to send data packets from the client computer to a server, you do not receive Internet Control Message Protocol (ICMP) "Destination Unreachable" messages when the data packets are larger than the Maximum Transfer Unit (MTU) size limit that is set on the server.

This problem may occur when either of the following conditions is true:

The client computer is using a dial-up connection or a virtual private network (VPN) connection.
The client computer is using an FTP server to transfer data.

For more information about the MS05-019 security update, click the following article number to view the article in the Microsoft Knowledge Base:

893066 MS05-019: Vulnerabilities in TCP/IP could allow remote code execution and denial of service

RESOLUTION

Hotfix Information

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 service pack that contains this hotfix.

To resolve this problem immediately, 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

To install this hotfix, you must be running Windows XP Professional SP2.

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.

File name	File version	File size	Date	Time
Ipnat.sys	5.1.2600.2774	135,296	11-Oct-2005	23:51

MORE INFORMATION

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

For more information about Internet Control Message Protocol, click the following article number to view the article in the Microsoft Knowledge Base:

170292 Internet Control Message Protocol (ICMP) basics

For more information about default Maximum Transfer Unit sizes, click the following article number to view the article in the Microsoft Knowledge Base:

314496 Default MTU size for different network topology