SQL Server 2005/2008 Windows Authentication - Not Associated with a Trusted SQL Server Connection Error

So you have setup SQL Server either version and from a separate box you are trying to access it using Windows Authentication as you rightly should. Doing so causes the proverbial “Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection" error, but you can happily login with basic SQL Server authentication.

 This is common in situation where you are using a DNS resolved hostname for the SQL server. Take for instance the server name is sqlsvr01 and the hostname you using is a different variation of that and is resolved via a DNS server as say db.domain.com. You can resolve this by creating an alias for the hostname on the client/source machine. This is accomplished in the SQL Configuration Manager utility under the SQL Server Native Client option.

Make sure to specify the port number, usually 1433 and also the IP address itself. This should enable SQL Server to authenticate in Windows Authentication mode and get rid of the “Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection" errors.