IIS binding limit (401.2 error)

Windows authentication process can take place on the user-mode (IIS worker process) or kernel-mode (HTTP.SYS). For the kernel-mode, there is a limitation: You can add maximum 64 bindings to your site. If you add 65 or more bindings, IIS displays “401.2 Unauthorized: Logon Failed Due to Server

Configuration with No Authentication” error even though the credentials are correct.

A change for Windows Server 2008 R2 or Windows Server 2012 R2 is not expected for this limitation.

Workaround

Use user-mode authentication for your application to get around binding limitation of kernel-mode.

Steps to use user-mode authentication instead of kernel-mode:

1. Open IIS Manager
2. Click on the website
3. Go to “Authentication“
4. Select “Advanced Settings”
5. Uncheck “Enable Kernel-mode authentication“

Continue with these steps:

1. Open IIS Manager
2. Click the website name
3. Go to “Configuration Editor“
4. Select “system.webServer/security/ authentcation/windowsAuthentication”
5. Set “True” for “useAppPoolCredentials“
6. Set “False” for “useKernelMode“
7. Click “Apply“

A discussion about the binding limit on IIS forum.