Why is Windows Authentication not working Locally but working Remotely?

Question

I've run into this issue on various Windows Servers: When logged into the server, IIS Windows authentication through a browser does not work for either Windows Auth or Basic Auth.

I have several sites set up with Windows authentication, and when I try to access them from the server I cannot log in. Not with just username or password, or domain+username/password.

However, accessing the same site externally and logging in works just fine, using my Windows log on credentials.

So - why can I not log in locally in this case?

More info:

• Server is not on a domain (single box)
• Using Chrome, but also tried with IE on the server same result
• Access via RDP, using an admin account
• IIS Basic Authentication fails the same way for application tasks

Answer 1

This is due to a security loopback protection built into Windows XP (and above).

Please see the other two SO answers here:

https://stackoverflow.com/questions/17466665/windows-authentication-not-working-on-local-iis-7-5-error-401-1

https://stackoverflow.com/questions/7387156/unable-to-get-windows-authentication-to-work-through-local-iis