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SQL Server login with Management Studio Fails with Error 18456

You’re attempting to manage an SQL Server 2008 instance with Management Studio but are receiving an error 18456 when using AD authentication.


Error “Token-based server access validation failed with an infrastructure error” (event id 18456).


Follow these steps to debug the issue:

  1. First, make sure that you are logged in as a user with SA privileges.  Management Studio will only use AD credentials of the current session; you cannot specify an AD user and password like you can for SQL Server Authentication
  2. Check the Application event log for the 18456 event:

    If the error is “Token-based server access validation failed with an infrastructure error” the mostly likely culprit is UAC.  Close Management Studio, right-click and select Run As Administrator.  You’ll probably be able to login at that point.


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