Fix ISA Server 2000 Web Browser Problems

This post describe How to fix Problems with Web Browser if ISA Server 2000 Is Chained to an Upstream Web Proxy Server. This contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs.

If Internet Security and Acceleration (ISA) Server 2000 is chained to an upstream Web proxy server, you may experience unexpected delays, incomplete pages, random authentication warning messages, and so forth, when you browse the Web.

This behavior can occur if all of the following conditions are true:

* The downstream ISA Server computer is configured to require integrated authentication (NTLM).

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* The upstream Web proxy server is not configured to require authentication (anonymous).

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* You are using Internet Explorer as your client browser.

Under certain circumstances, Internet Explorer sends an extraneous NTLM authentication header on a connection that has already been authenticated with the downstream ISA Server computer by using integrated authentication. This may cause the downstream ISA Server computer to pass those credentials to the upstream Web proxy server. Because these credentials are for the downstream ISA Server computer, the upstream proxy server may return unexpected delays or responses because it is unable to process the NTLM credentials. The downstream ISA Server computer then passes this HTTP response back to the Web browser, resulting in unexpected delays, authentication warning messages, or other effects on the client computer (running Internet Explorer).

Note that you must have ISA Server 2000 Service Pack 1 (SP1) installed on your computer before you apply the following fix.

For additional information about how to obtain ISA Server 2000 SP1,
How to obtain the Latest Internet Security and Acceleration Server 2000 Service Pack

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this post. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To implement the functionality in this fix and then enable it, follow these steps after you have installed the fix:

1. Stop the Web Proxy service.
2. Start Registry Editor.
3. Locate and select the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3Proxy\Parameters
4. Create a new DWORD value named RemoveAllProxyAuthorization. Give this new value a data value of 1.
5. Restart the Web Proxy service.

To revert to the original configuration, either remove the RemoveAllProxyAuthorization registry value or change its data value to 0 (zero). After you make either change, restart the Web Proxy service.

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