By default, Mozilla Firefox does not pass NTLM authentication to a web server. Follow the steps below to configure Firefox to pass NTLM authentication to certain trusted sites:

1. Open Firefox and type about:config in the address bar and press Enter
2. In the Search field type network.automatic-ntlm-auth.trusted-uris and press Enter
3. Double-click on network.automatic-ntlm-auth.trusted-uris
4. In the dialog box that comes up enter the URLs of the sites you wish to pass NTLM authentication info to in the form of http://PVEAuthGW:81

Note: You can add more than one website to this dialog box by separating them with a comma.