Overview

This article describes the process to follow when the below error message is displayed after trying to browse to a website:

Error 502: Failed Connection Attempt ISA 04/03/2012 11:54:00 AM Log type: Web Proxy (Forward) Status: 50 The request is not supported. Rule: Allow Internet Access Source: Internal ( 10.0.80.50:0) Destination: External ( 184.85.5.36:80) Request: POST

Information

Environment

• GFI WebMonitor for ISA / TMG 
• Microsoft ISA server 2004
• Microsoft ISA server 2006

Root Cause

When the compression filter is disabled, Microsoft ISA cannot handle some compressed HTTP content.

Process

To correct the issue, you much enable the HTTP Compression Filter:

1. Open the Microsoft ISA Management MMC.
2. Expand the Configuration node.
3. Under the General node, click on Define HTTP Compression Preferences.
4. Click on Add and select the Network and/or Computer sets you wish to apply the compression rules to.
5. The default compression level is disabled. Select an element and press the Set Compression button to configure compression.