SQL Server connection user varies when using '127.0.0.1' vs 'localhost'. Why?

• jaredcrain

  SSC Enthusiast

  Points: 184

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  January 7, 2019 at 8:07 am

  #381118

  When I attempt to connect to my local, default SQL Server instance via SQL Management studio using Windows Authentication, I successfully connect when I use Server Name "localhost", but fail when I use Server Name "127.0.0.1". With login auditing enabled for both failed and successful logins, I see that the successful logins are recorded as:

  Login succeeded for user 'AzureAD\RealUsername'. Connection made using Integrated Authentication. [CLIENT: <local machine>]

  And the failed logins are recorded as:

  Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'. Reason: Could not find a login matching the name provided. [CLIENT: 127.0.0.1]

  Possibly relevant:

  • I can connect using the ip address if I use SQL Server authentication (since I am forcing it to use an existing login).
  • There is no entry in my hosts file for "localhost", and when I ping localhost it does resolve to 127.0.0.1.
  • The SQL instance uses port 1433.
  • The issue, with very little variation, persists when connecting via SQL Management Studio, a .NET web app running in a local IIS instance, or via UDL file on my desktop.

  
  Here is my question: Why would changing only the server value ('localhost' vs '127.0.0.1') change the identity used when connecting?

• x

  SSC-Insane

  Points: 23660

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  January 16, 2019 at 12:39 pm

  #2019134

  possibly related:

  https://support.microsoft.com/en-us/help/303650/intranet-site-is-identified-as-an-internet-site-when-you-use-an-fqdn-o