Mixed Mode Authentication in .NET

In my current project, we need both internal and external users to access the application. Ideally, for internal users, there shouldn't be any login required. To handle such a case, I was looking for some useful links and found the following to be useful:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspp/html/mixedsecurity.asp
http://aspalliance.com/553
Though the approaches are a bit different but they accomplish the same thing. I am more confident about the first approach.