After performing all configurations above, you need to enable the Negotiate authentication of Firefox in client machines so that clients could be authenticated by GateIn 3.2 as follows:
Start Firefox, then enter the command: about:config into the address field.
Enter network.negotiate-auth and set the value as below:
network.negotiate-auth.allow-proxies = true network.negotiate-auth.delegation-uris = .local.network network.negotiate-auth.gsslib (no-value) network.negotiate-auth.trusted-uris = .local.network network.negotiate-auth.using-native-gsslib = true
Consult documentation of your OS or web browser if using different browser than Firefox.