The Web Proxy Filter in ISA Server 2004 may log requests with an incorrect access rule when you use overlapped HTTP protocols (917051)


The information in this article applies to:

  • Microsoft Internet Security and Acceleration Server 2004 Service Pack 2, when used with:
    • Microsoft Internet Security and Acceleration Server 2004, Enterprise Edition
  • Microsoft Internet Security and Acceleration Server 2004 Service Pack 1, when used with:
    • Microsoft Internet Security and Acceleration Server 2004, Standard Edition
  • Microsoft Internet Security and Acceleration Server 2004, Enterprise Edition
  • Microsoft Internet Security and Acceleration Server 2004, Standard Edition

SYMPTOMS

When you use overlapped HTTP protocols on a Microsoft Internet Security and Acceleration (ISA) Server 2004 computer, you may find that the Web Proxy Filter logs requests that have incorrect references. For example, the Web Proxy Filter may log requests that have references to the default access rule instead of to the access rule that is configured to enable HTTP protocols.

Note When you use overlapped HTTP protocols in ISA Server 2004 Enterprise Edition-based computers, the requests that are logged may have references to the Enterprise default rule.

CAUSE

This problem may occur because the Web Proxy Filter in ISA Server 2004 incorrectly sets the logging field to the last rule that is processed. This typically occurs when multiple definitions exist for the same port.

RESOLUTION

A fix is available for computers that are running ISA Server 2004 Service Pack 2 (SP2). To resolve this problem, install the hotfix that is described in the following Microsoft Knowledge Base article:

916106 Update for HTTP issues in Internet Security and Acceleration Server 2004 Service Pack 2

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

MORE INFORMATION

Overlapped HTTP protocols are used when you have to prevent the Web Proxy Filter from intercepting the Web traffic. This configuration may be required when non-standard HTTP traffic uses TCP port 80. If you use the standard HTTP protocol, the traffic may be denied if it does not comply with the RFC standard.

To enable non-standard HTTP traffic in this scenario, the custom HTTP definition must not be bound to the Web Proxy Filter.

To use overlapped HTTP protocols, you must deny the HTTP protocol for sites where a custom HTTP protocol is used. This is to make sure that ISA Server 2004 chooses the correct protocol.

For example, if a virtual private network (VPN) client has to use the custom HTTP protocol to connect to an internal server, the rule that enables the custom HTTP protocol must have a higher priority than the rule that enables the standard HTTP protocol. You must also configure a rule to deny the standard HTTP protocol to the internal server to make sure that the custom HTTP protocol is used.

The following table lists the rules that have to be configured to enable traffic in this scenario:
PriorityRule NameProtocolFromTo
1Allow HTTP (No Proxy) to Custom HTTP ServerHTTP (No Proxy)VPN ClientsCustom HTTP Server (Computer object)
2Deny HTTP to Custom HTTP ServerHTTPVPN ClientsCustom HTTP Server (Computer object)
3Allow HTTP to other sitesHTTPVPN ClientsOther Internal Web Servers (Computer Set object)
Note The third rule is configured to enable HTTP to other sites.
Modification Type:MajorLast Reviewed:5/23/2006
Keywords:kbQFE kbBug kbprb KB917051 kbAudITPRO
©2004 Microsoft Corporation. All rights reserved.