Group Policies may not apply because of network ICMP policies

When you use Group Policy to determine whether a link is fast or slow, fast links may be incorrectly flagged as slow links.

You may recieve the following error message when this issue occurs:

This problem may occur when a network that you are trying to detect a slow link to is configured to control the size and flow of Internet Control Message Protocol (ICMP) packets. For example, if a router allows for only ICMP ping packets that have a size of 1,024 bytes, the slow-link detection feature may flag the connection as a slow link. This is because the router discards ICMP packets that are larger than 1,024 bytes. If the router discards the packet because it exceeds the allowed size, fast links may be reported as slow links.

The Microsoft Knowledge Base article that is listed in the "More Information" section describes how slow link detection works. On Microsoft Windows 2000-based computers or Windows XP-based computers that do not have the hotfix that is described in this article installed, the client computer pings a domain controller three times with a zero-byte packet. If the response time is more than 10 milliseconds (ms), the client computer then pings with packet size of 2048.If the larger ping response time is more than 10 ms, this indicates a slow link. If the results of this procedure indicated a slow link all three times, then the link is flagged as a slow link.

To resolve this problem, configure Windows to use smaller ICMP ping packets for fast-link detection. The hotfix described here enables configuring a custom ICMP ping packet size.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

Windows Server 2003

Service pack information

To resolve this problem, obtain the latest service pack for Windows Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Windows XP

Service pack information

To resolve this problem, obtain the latest service pack for Windows XP. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

A supported hotfix is 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 software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if 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. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Restart requirement

You must restart your computer after you install 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 tool in Control Panel.

Windows 2000

Service pack information

To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

A supported hotfix is 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 software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if 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. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

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 tool in Control Panel.

Installation notes

After you install this hotfix, you can resolve the symptom that is described in this article by configuring Windows to use a smaller ICMP ping packet size. To manually change the ICMP ping packet size, create the following registry subkey:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Windows Server 2003

This problem was first corrected in Windows Server 2003 Service Pack 1.

Windows 2000

This problem was first corrected in Windows 2000 Service Pack 4.

Administrators can use fast link detection to control the application of Group Policy to slow links. This functionality uses ICMP to determine whether a link is fast or slow. For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the following article number to view the article in the Microsoft Knowledge Base: