You can configure Internet Explorer to use the Automatic Proxy Discovery functionality over Dynamic Host Configuration Protocol (DHCP). This option can direct Web clients to ISA Server's Web proxy service through Web Proxy Autodetect (WPAD) process. In Microsoft Windows 2000, this feature works only for users who are member of the Administrators or Power Users group. In Microsoft Windows XP, the Network Configuration Operators group also has permission to issue DHCP queries.

DHCP client calls are implemented over a RAW named pipe. For security reasons, specific permissions are set on the named pipe. In Windows 2000, an access control entry (ACE) is set on the pipe for the Administrators and Power Users groups. In Windows XP, an ACE is also set for the Network Configuration Operators group.

Microsoft Windows 2000

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: 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.

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.

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   08-Jul-2003  01:27  5.0.2195.6770      89,360  Dhcpcsvc.dll     

Microsoft 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 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: 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.

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.

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   29-Mar-2004  09:20  5.1.2600.1351     103,936  Dhcpcsvc.dll     

To work around this behavior, use one of the following methods:

•	Make sure that the appropriate user belongs to one of the groups that are listed in the "Symptoms" section of this article.
•	Use an automatic configuration script instead of Automatic Proxy Discovery.

This behavior is by design. This problem was corrected in Microsoft Windows XP Service Pack 2.

For more information about how to configure Automatic Proxy Discovery, click the following article number to view the article in the Microsoft Knowledge Base: