Consider a site used for an intranet which should also be accessible from the internet. On the intranet you want to use Windows Authentication and on the internet you want the users to access the site using forms authentication.
Is it possible to set up a mixed-mode with these two? I just want to validate that the user is logged in with either of them without using two sites.
You may want to look at a similar question: mixed mode authentication against AD and fallback to the database if it fail with Membership providers
In the answer I posit a solution using a facade. I have leveraged this approach to integrate AD on multiple domains, aspnet sql provider and a legacy authentication database with measurable success.