I\'m running MVC3 and a windows auth web application. When I deploy to IIS6 it runs great until I hit a page that requires authentication. It then is auto-redirecting to /
I know this is a super old post. But I just ran across this after going through a tutorial on upgrading from MVC 4 to MVC 5. So I'm throwing it on just in case anyone else makes the mistake I did. My issue ended up being that I accidently added 'Microsoft.AspNet.WebPages.WebData' to my project while upgrading my references.
Running "Uninstall-Package Microsoft.AspNet.WebPages.WebData" restored my authentication to it's previous glory.