Microsoft KB Archive/938465

= Error message when you try to access Web sites through a downstream server after you enable hotfix 927265 on an upstream server that is running ISA Server 2004: &quot;502 Proxy Error&quot; =

Article ID: 938465

Article Last Modified on 12/4/2007

-

APPLIES TO


 * Microsoft Internet Security and Acceleration Server 2004 Standard Edition
 * Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition

-



SYMPTOMS
Consider the following scenario:  A downstream server is chained to an upstream server that is running Microsoft Internet Security and Acceleration (ISA) Server 2004. A client computer is configured to use the downstream server as the proxy server. On the upstream server, you have enabled the hotfix that is described in the following Microsoft Knowledge Base article:

927265 Authentication fails when client computers use Internet Explorer 7 to authenticate with an upstream ISA Server computer through a downstream ISA Server computer that does not require authentication



However, when a user on the client computer tries to access Web sites through the downstream server, the user receives the following error message:

Error Code: 502 Proxy Error. Logon Failure: Unknown user name or bad password. (1326)



CAUSE
This problem occurs because proxy-to-proxy authentication fails. The downstream server expects the upstream server to return &quot;Negotiate&quot; as a supported authentication scheme for Windows Integrated authentication. However, after you enable hotfix 927265, the upstream server is configured to return only &quot;NTLM&quot; as an authentication scheme for Windows Integrated authentication. Therefore, the downstream server and the upstream server cannot authenticate one another.



RESOLUTION
A hotfix package is available to resolve this problem. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

938466 Description of the Internet Security and Acceleration Server 2004 hotfix package: June 5, 2007



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
The authentication process between the downstream server and the upstream server uses a special URL request. After you apply hotfix 938466, the upstream ISA Server computer will return &quot;Kerberos&quot; and &quot;Negotiate&quot; as supported authentication schemes if there is a special ISA-to-ISA authentication URL request.

Keywords: kberrmsg kbtshoot kbprb kbexpertiseinter KB938465

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.