Client requests to access a published Web site are blocked when you configure ISA Server 2006 to allow direct authentication to access a published Web server

You configure a computer that is running Microsoft Internet Security and Acceleration (ISA) Server 2006 to use pass-through authentication to access a published Web server. After you do this, all client requests to access the published Web site are blocked. Additionally, you may receive an error message that resembles the following:

Error Code: 403 Forbidden. ISA Server is configured to block HTTP requests that require authentication. (12250)

  • You experience this issue when you use the No delegation, but client may authenticate directly (pass-through) authentication method.
  • This issue may occur even if the ISA Server 2006 computer publishes a site that requires no authentication.

This issue may occur if the following conditions are true:

  • The Allow client authentication over HTTP check box in the Web listener’s Advanced Authentication Options dialog box is not selected.
  • The Web listener is not enabled to listen for Secure Sockets Layer (SSL) requests.

For the solution, check out the KB article here:



Thomas W Shinder, M.D.


Email: [email protected]

MVP — Microsoft Firewalls (ISA)

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