Sometimes when we try to connect to MS SQL Server database, it does not connect and throws up an error that says:
This error is received when connection request is being sent to server but due to some reasons it is not able to accept it. You can determine the true reason for this SQL error 18456, by checking server's error log where corresponding entries are maintained.
Example:-
2014-05-06 00:02:00.34 Logon Error: 18456, Severity: 14, State: 8.
2014-52-06 00:02:00.34 Logon Login failed for user '(user name)'. [CLIENT: (ip address)]
The word "State" in the message states the accurate sources of problem which are responsible for rising of SQL Server error 18456. In this type of error message the state indicates a no's like 1, 2,3,5,6,7,8,9,11,12,13,18. These numbers shows the reasons of the occurrence of this error 18456 by which you can correct it.
Such types of error creates a serious trouble like situations which can be resolve by external SQL password recovery software. This software prudentially solves SQL Server login failed 18456 and its different state levels without any harm. Using this software you can ultimately login in SQL SA and User account and execute operation on the SQL database.