The Claims Authentication Riddle - Part 2

Following up on my earlier post, here’s the latest installment of my Riddle of the Three Failing SharePoint 2010 FBA Web Applications.  As you’ll recall, I’ve been experiencing some baffling authentication errors with SharePoint Claims Authentication web apps which prompted me to configure a “clean room” test on a VM that consisted of three vanilla publishing web apps, each set up for claims auth using a standard ASP.NET SQL Membership database.

What I discovered was that as I configured the web apps, things began to fail once I completed setting up the last one.  I found that the second web app wouldn’t let me in, then the first then all three.  For no apparent reason.

I escalated this to open a support ticket with Microsoft on the issue, which is ongoing.  However, I did want to show what we’re seeing as it is a variant on the above scenario.  Support believed the issue could be with the way we were configuring our connection strings and providers through IIS Manager, and recommended using modifications to web.config.  Six and one half dozen, I think, but ok.  Then things got weird.

So – same deal:  Three web apps, port 80, 85 and 90.  This time, port 90, the last one configured, works as advertised - solid.  The first two fail in a strange way where accessing one affects the other requiring authentication using Windows credentials and signing in as an FBA user once access is granted.  Sign out, however, and your FBA creds get denied.

The following screencast shows what we’re seeing – again, if you can set up a similar test environment to corroborate or refute, this would be helpful!  We’re running the RTM code and back-ended to a SQL 2008 R2 database.