Today I found myself in the following scenario; I had created a new Web Application with an authentication type of Claims Mode, and just using Windows Integrated Authentication (NTLM). I then extended the web application to a new zone (on which I was going to enabled Forms based authentication). To my surprise, when I tried to set the Authentication Provider I wasn’t given any option other than Windows Integrated, it looked more like the Web App was in Classic Mode authentication. Running the PowerShell below on the URL of my extended zone gave me the option in SharePoint to select Forms Based authentication as I was expecting.
$App = get-spwebapplication “http://vs-server95:102”
$app.useclaimsauthentication = “True”