Use the FQDN of the Proxy Server when you use Kerberos authentication
If you use Kerberos authentication together with Squid Proxy Server remember to use the FQDN (Fully Qualified Domain Name) of the Proxy Server in your browsers proxy settings .
Kerberos authentication will not work if you use just the IP address (eg 192.168.1.250) or just the hostname (squid instead of squid.contoso.com) of the proxy server.