Additional properties are now available for logging in the Httperr#.log file in IIS 6.0 and IIS 7.0

The Httperr#.log file logs all invalid requests. This behavior separates these requests from the IIS W3svc log file. However, by default, the Httperr#.log file does not contain the same fields that are available in the World Wide Web Consortium (W3C) Extended Log file format.

The Httperr#.log file enables IIS to log invalid requests separately from valid requests. Both logs are used to log information about client requests that are made to the Web server. However, IIS log entries are created when the send has completed. The error logging occurs after the driver has initiated the send but before the send has completed. Therefore, not all fields that can be logged in the W3C Extended Log file can be logged in the Httperr#.log file.

This software update makes these fields available in the Httperr#.log file. If the computer is running Windows Server 2003 Service Pack 1 (SP1) or a later version, Windows Vista, or Windows Server 2008, no software update is required. Just make the registry changes that are explained in this article.

Software update 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 software update 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.

Implementation information

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

After you apply this software update, create the following registry key: The new value in the registry controls the log fields that Http.sys error logging generates. By default, this value is the bitwise ORed value of the bit values of the default fields that are listed in the following table.

If you set the wrong field value, or if you set the field value to zero, or if the registry parameter is not present, the Http.sys parser uses the default fields. The bit value for each log field that is available is listed in the following table. To log all available fields, set the value of the ErrorLoggingFields registry key to 7DFF4E7 (hexadecimal).

To customize the fields that are logged, open the Windows Calculator, view the scientific version of the calculator, and then enter the hexadecimal values in the following table. Use the OR function to combine the values.

Note If you change the error logging configuration, you must restart the Http.sys parser. Note This software update also adds W3C header information to the Httperr#.log file.

Microsoft Internet Information Services (IIS) version 5.0 does not implement the concept of an error log. IIS 5.0 logs invalid requests and valid requests in the same Web log file. IIS 6.0 and IIS 7.0 improve on this design by by providing a separation between valid and invalid requests. You can merge the events in the IIS Web logs and in the Httperr#.log file sequentially to create a consolidated view that is similar to the W3C logs in IIS 5.0.

When an HTTP 400 Bad Request is logged, this error implies that the request did not comply with HTTP RFC 2616. Therefore, everything in the header is treated as suspicious and invalid.

When the Http.sys parser experiences an error while parsing a URL, fields such as user-agent and referrer will not be available. The fields that are not available are logged as dashes (-) in the Httperr#.log file. Sometimes, a request can be fully parsed but can still be logged in the error log file for errors other than parsing. These errors may include timeouts or malformed requests that cause the IIS worker process to fail. When this behavior occurs, fields such as user-agent and referrer are available.

After you apply this software update, you must add an entry to the registry and then set its value appropriately before you can configure the list of fields that are available to log in the Httperr#.log file. By default, the field combination is the same field combination that is included with Windows Server 2003. However, some W3C Extended Log file fields are not available for error logging.

The following table compares error logging and IIS W3C Extended Log file logging. Unless otherwise noted, the interpretation and the values of the fields the same.

Note The new fields that this software update adds to error logging appear as bold text.

For more information about the naming schema for Windows software updates, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the terminology that is used to describe Microsoft product updates, click the following article number to view the article in the Microsoft Knowledge Base: