As of this morning we have had thousands of failed login attempts to our SQL Server 2012 box.

Error :

Login failed for user 'Domain\User'. Reason: Infrastructure error occurred.
Check for previous errors. [CLIENT: 10.xxx.xxx.xxx]

Error: 18456
Severity: 14
State: 1

I have checked all the logs, permissions, and scoured forums for help on this issue but to no avail.

Server Login & Database User accounts are enabled
Server Login is mapped to the database that it has access too
Windows & SQL Server Authentication is applied
SA account is enabled
No orphaned users
etc etc...

Any ideas ?

  • Are there any other errors in the error log, such as SSPI errors? I appreciate that with thousands of errors, there's a lot to look through. Commented Nov 18, 2015 at 12:29
  • there are not unfortunately. All just "Login Failed" and "Error: 18456". this is why im having such an issue Commented Nov 18, 2015 at 12:40
  • Look at aaron's blog. sqlblog.org/2020/07/28/troubleshooting-error-18456 Maybe it can help you. Or you can trace with user errors to see what's going on.
    – Racer SQL
    Commented Nov 18, 2015 at 12:53
  • Unlike the error message that is returned to you, if you look at the error log you will see that specific State numbers will describe your problem. So, do look at Aaron's blog post.
    – RLF
    Commented Nov 18, 2015 at 14:42

2 Answers 2


The box lost connection to the domain controller, hence the login issues


As per MSDN BOL http://blogs.msdn.com/b/sql_protocols/archive/2006/02/21/536201.aspx The message is kept fairly nondescript to prevent information disclosure to unauthenticated clients. In particular, the 'State' will always be shown to be '1' regardless of the nature of the problem. To determine the true reason for the failure, the administrator can look in the server's error log where a corresponding entry will be written.

If the server encounters an error that prevents a login from succeeding, the client will display the following error mesage.

Msg 18456, Level 14, State 1, Server <server name>, Line 1
Login failed for user '<user name>'

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