I have MVC 4 website, where are 4 access points :
I have a website with similar domain extensions, including the https protocol, I forwarded all other domains to https://www.domain.com, its good for SEO reasons as well and for your analytics, I would suggest forward all domains to one single domain.
This answer also says:
So, how to share the authentication cookie across multiple domains? Well, there is absolutely no way to do that. The fundamental barrier of the HTTP protocol prevents you from sharing a cookie across different domains, primarily for security reasons.
...There is no built-in mechanism in ASP.NET to implement a Single Sign On across these two different sites.
You can redirect the website using web.config file by setting up sites in IIS to the redirect folder:
<?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <httpRedirect enabled="true" destination="https://www.domainname.com$S$Q" exactDestination="true" httpResponseStatus="Permanent" /> </system.webServer> </configuration>