As you may already know, there is 2 different authentication providers in SharePoint 2010:
- Classic Mode Authentication: the ‘old’ authentication providers. Used for standard Windows (NTLM, Basic or Kerberos) authentication
- Claims Based Authentication: the ‘new’ one. Used to allow Form Based Authentication
When you create a new web application, you have to choose between these 2 authentication methods.
But once the web application has been created, you can’t change it from the Central Administration site.
So, if you want to change the authentication method to use you have to delete and then recreate the web application.
Good news, with PowerShell, you can switch from Classic Mode to Claims Based. Switching from Claims Based to Classic Mode is not possible.
To switch from classic to claims, open a session on a SharePoint server and launch the PowerShell for SharePoint 2010 (SharePoint 2010 Management Shell)
Then run the following commands
$app = Get-SPWebApplication <replace with your web application URL>
$app.UseClaimsAuthentication = "True"
Et voilà, you have switched from classic mode to claims based