Web Proxy Access Control Fails When Set Up on IIS 4.0

The information in this article applies to:

• Microsoft Proxy Server version 2.0
• Microsoft Internet Information Server version 4.0

SYMPTOMS

If you set up Proxy Server 2.0 on Internet Information Server (IIS) 4.0 (either as an upgrade or new setup), and you select (enable) access control with a valid user account, the Web Proxy clients may fail to connect and display one of the following error messages:

NOTE: The error message depends on the browser you use.

Microsoft Internet Explorer version 4.0 and 4.01:

   Nothing returned to browser (no error or blank page)

   The requested header not found.

   Document contains no data.

CAUSE

This is caused by a problem with the authentication settings with IIS 4.0 and the Web Proxy ISAPI filter.

WORKAROUND

Use one of the following methods:

Method 1

Disable Access Control in Web Proxy Service by opening the Web Proxy Properties within the MMC and go to the Permissions tab. Clear the Enable Access Control check box.

Method 2

Disable Anonymous access for the default web site in IIS 4.0.

NOTE: This will enable Proxy clients to connect to the Internet; however, it does not allow anonymous users to connect to the default web site if the server is also used for Internet publishing.

Method 3

Do Method 2 and make the following IIS configuration changes to allow anonymous users access to your web site.

a. Bind a second valid IP address to the external interface of the

   Proxy/IIS computer.

c. Assign the new IP address to the new web site.

d. Select the Anonymous access box during web site creation.

NOTE: This configuration will allow Anonymous Internet users to view web pages on the server and allow proxy users to authenticate before connecting to the Internet. In addition, it requires that an additional valid Internet IP address is obtained from the Internet Service Provider.

Once these steps are completed, the second web site can be created. Please see the IIS 4.0 online documentation for additional information.

To add multiple IP addresses in Microsoft Windows NT Server version4.0:

1. Obtain a valid second Internet IP address.

2. Right click Network Neighborhood.

3. Click Properties.

4. Click Protocols.

5. Double-click TCP/IP Protocol.

6. With external adapter active in the dropdown list, click the Advanced button.

7. In the Addresses box, click the Add button and then add the second IP address you got from the ISP and provide the correct subnet mask.

8. Click OK four times.

9. Reboot the computer.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Proxy Server version 2.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.