With IIS 7, came the Failed Request Tracing which facilitates debug logging. Its gives a detailed report and you can understand why common errors (like HTTP 400, 401, 500, etc.) occur. Failed request tracing is not enabled by default but is easy to configure. It is recommended to disable the tracing after you fix the problem; else it will unnecessarily take up the disk space.
Note: Before you make any change, always backup IIS.
To Backup IIS,
. Open an elevated command prompt (Run as Administrator…) and run the following command:
Enable Failed Request Tracing at the Server node (will capture Failed Requests for all the websites in IIS):
· At the server node, go to “Failed Request Tracing Rules”
· Add\All content (*)\Next
· Choose the Status code(s) you are troubleshooting (404, 500, etc)
· Complete the wizard
To Enable Failed Request Tracing on the Website having issues:
· Manage Web Site\Configure\Failed Request Tracing…
The log can be accessed from, %SystemDrive%\inetpub\logs\FailedReqLogFiles.
Always remember to disable the logging after the problem is fixed so that the logs do not keep filling the disk.