This post shares some of the things where Internet Explorer Kerberos authentication fails. It is important to understand the default behavior of Internet Explorer and its support for Kerberos authentication so that you don’t start ripping out your hair (can’t speak to what Ned does here). I have listed three very common problems that we typically see when Kerberos authentication is failing with web-based applications: Website does not use the standard TCP/IP port of (80/443); CNAME DNS RR is used for a website; Website works on first access but starts failing 30 minutes later

Full Article: DS Blog