title: Method for Sharing Forms Authentication Login between MVC.net and Web API Sites on the Same Domain
body: <p>I am going to have an ASP.net MVC web site (example.com) and a Web API site (api.example.com) running on the same domain. What is the best and most secure way to use Forms Authentication to allow a user to log in to the MVC site, and have that login accepted by the <code>[Authorize]</code> filter in the API site? Additionally, there is the possibility that both sites will be hosted on multiple servers (each of which might have its own subdomain), so a solution that would allow for a single sign on approach to work among all of the servers in the cluster would be preferred. </p>