Troubleshooting HTTP 401 errors in IIS

IIS Support Voice column

To customize this column to your needs, we want to invite you to submit your ideas about topics that interest you and issues that you want to see addressed in future Knowledge Base articles and Support Voice columns. You can submit your ideas and feedback using the Ask For It form. There's also a link to the form at the bottom of this column.
Hello. My name is Lou Prete. I have been supporting Microsoft Internet Information Services (IIS) for the past five years and have been IIS content lead for the past two years.

HTTP 401 errors are among the most common errors you may have to deal with in IIS. While the causes for these errors can vary greatly, the causes fall into a finite number of categories. Correctly identifying the category of the cause for your HTTP 401 error can decrease the amount of time needed to identify the root cause of the error.

This article describes the troubleshooting steps when you encounter HTTP 401.x errors (401.1, 401.2, 401.3, 401.4, 401.5) in Microsoft Internet Information Services (IIS):

Troubleshooting steps

For IIS 6.0 or the later versions of IIS 6.0

Starting in IIS 6.0, the substatus code is logged in the
Web logs. The Web logs are located in the following location:
%SYSTEMROOT%\System32\LogFiles\W3SVC###\
In the Web logs, the last three numbers in each entry represent
the status, the substatus, and the Win32 status.
#Fields: date time s-sitename s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) sc-status sc-Sub-status sc-win32-status2006-03-06 20:37:42 W3SVC1 192.168.1.101 GET /default.aspx - 80 - 192.168.17.45 Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.1;+SV1;+.NET+CLR+1.1.4322;+.NET+CLR+2.0.50727;+InfoPath.1) 401 2 21480742542006-03-06 20:37:42 W3SVC1 192.168.1.101 GET /default.aspx - 80 - 192.168.17.45 Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.1;+SV1;+.NET+CLR+1.1.4322;+.NET+CLR+2.0.50727;+InfoPath.1) 401 1 02006-03-06 20:38:36 W3SVC1 192.168.1.101 GET /default.aspx - 80 DOMAIN\user 192.168.17.45 Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.1;+SV1;+.NET+CLR+1.1.4322;+.NET+CLR+2.0.50727;+InfoPath.1) 200 0 0

For the earlier versions of IIS 6.0

Useful tools and resources

  • WFetch
    284285 How to use Wfetch.exe to troubleshoot HTTP connections

  • Network Monitor
    148942 How to capture network traffic with Network Monitor

  • Auditing/Security log
    300549 How to enable and apply security auditing in Windows 2000

Third-party solution disclaimer

The information and the solution in this document represent the current view of Microsoft Corporation on these issues as of the date of publication. This solution is available through Microsoft or a third-party provider. We do not specifically recommend any third-party provider or third-party solution that this article might describe. There might also be other third-party providers or third-party solutions that this article does not describe. Because we must respond to changing market conditions, this information should not be interpreted as a commitment by Microsoft. We cannot guarantee or endorse the accuracy of any information or of any solution that is presented by Microsoft or by any mentioned third-party provider.

Microsoft makes no warranties and excludes all representations, warranties, and conditions whether express, implied, or statutory. These include but are not limited to representations, warranties, or conditions of title, non-infringement, satisfactory condition, merchantability, and fitness for a particular purpose, with regard to any service, solution, product, or any other materials or information. In no event will Microsoft be liable for any third-party solution that this article mentions.Until next time, thank you for your time, and have a great day. As always, feel free to submit ideas on topics you want addressed in future columns or in the Knowledge Base using the Ask For It form.

Properties

Article ID: 907273 - Last Review: Feb 14, 2017 - Revision: 1

Microsoft Internet Information Services 6.0, Microsoft Internet Information Server 1.01

Feedback