To determine the authentication method of your connection use...
SELECT net_transport,
auth_scheme,
encrypt_option,
last_read,
client_net_address,
local_net_address
FROM sys.dm_exec_connections
WHERE session_id = @@SPID;
"You must run this on a client machine and not on the SQL Server you are testing, otherwise it will come back as NTLM even if Kerberos is properly configured. This is due to per-service SID security hardening added in Windows 2008, which makes all local connections use NTLM regardless of whether Kerberos is available."(1)For info on all connected sessions use...
SELECT a.session_id,
b.connect_time,
a.login_time,
a.login_name,
b.protocol_type,
b.client_net_address,
b.auth_scheme,
a.HOST_NAME,
a.program_name
FROM sys.dm_exec_sessions a
JOIN sys.dm_exec_connections b
ON a.session_id = b.session_id
ORDER BY b.client_net_address
Or...
SELECT s.session_id,
s.original_login_name,
c.net_transport,
c.auth_scheme,
c.local_net_address,
c.local_tcp_port,
s.program_name
FROM sys.dm_exec_sessions s
LEFT OUTER JOIN sys.dm_exec_connections c
ON (s.session_id = c.session_id)
WHERE s.is_user_process = 1
SQL Server will attempt to register a Service Principal Name on startup of the SQL Server service but will fail to do so unless any one of the following is true...
The SQL Server service account is a domain admin
The SQL Server service account has been granted the Write servicePrincipalName permission
The SQL Server service account is NT Service/MSSQLServer