Most of the applications nowadays relies on IIS and you could face a lot of issues with access authentication and authorization.

Luckily Microsoft have a very nice tool you can use to help you diagnose and get to the root cause of the issue.

the tool is called Authentication and Access Control Diagnostics 1.0 and can be downloaded from here (X86) (X64)

The AuthDiag tool is designed to help you when you see either of the following error messages:

  • 401.1 logon failed
  • 401.3 ACL

The AuthDiag tool can also help you when you experience Kerberos problems.

And this is a sample of what this tool can help you do