How can I know whether my SharePoint 2010 Web Application is using NTLM or Kerberos authentication?
Download Fiddler and Run it. Fire up your IE and open the SharePoint site in the browser. Now go back to Fiddler and see the traces. Click on the trace with a HTTP Response headers pane in the left. If Kerberos is working "Cookies / Login" will show Authorization:Negotiate.
A detailed walkthrough is here
This ofcourse goes with the assumption, that you do not have access to the Central Admin.
Incase you have access to the Central Admin, Open the CA in browser. Click Manage Web applications > Select your web application > Authentication Provider (Ribbon option) > Click on Default(Zone Name) > IIS Authentication Settings.
If you have access to your IIS server that is another option and much simpler than inspecting HTTP traffic: Simply view the site Authentication module config for Windows Authentication.
- In IIS Manager
- Select your site
- Click on the Authentication module
- Select Windows Authentication
- Select Providers...