Article ID: 271361 - View products that this article applies to.
This article was previously published under Q271361
When you configure Internet Explorer to use an automatic proxy configuration script, it caches the proxy that is returned by the FindProxyForURL call. The caching mechanism (Automatic Proxy Result Cache) is performed on a host basis (that is, not on an URL basis). This prevents you from using different proxies to gain access to the same Web server. The following sample scenario demonstrates this behavior:
The Automatic Proxy Result Cache is a performance enhancement that was added to Internet Explorer 5.5 and later. The purpose of the cache is to reduce the client-side processing of the automatic proxy configuration script. When you connect to an Internet site, the FindProxyForURL function is used to determine whether a proxy should be used and which proxy to use. Internet Explorer 5.5 and later first checks the Automatic Proxy Result Cache to determine whether a proxy was used to connect to the host on previous attempts. If this checks fails, it indicates that this is the first attempt to connect to the host during the current session and the normal proxy detection logic applies. The following list illustrates the logic Internet Explorer 5.5 and later uses to determine whether a proxy should be used and which proxy to use:
When a connection is established through a proxy server, the host name of the site and the proxy server name are cached. On future attempts to access the host name in the same session, Internet Explorer has cached information about which proxy to use. Therefore, all subsequent connections to the host are tried through the proxy that was used previously. This means that if the proxy server name that is cached is unavailable during the same session, the automatic proxy configuration script is not re-processed, and you receive a "Page Cannot Be Displayed" error message in Internet Explorer.
You may want to disable the Automatic Proxy Result Cache to provide the proxy redundancy that you require. This will result in client-side processing of every GET request that is issued by Internet Explorer. As a result, Internet Explorer performance may be impacted depending on the logic of the Automatic Proxy Configuration Script and its size. To disable the Automatic Proxy Result Cache, use one of the following methods.
Note If you disable automatic proxy caching, Internet Explorer performance may be affected.
Method 1: Modify the registryImportant This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
You can disable the Automatic Proxy Result Cache by using the following registry key:
If the registry key is not present, you can create the registry key by using the following registry file:
Data value: 0 = disable caching; 1 (or key not present) = enable automatic proxy caching (this is the default behavior)
Windows Registry Editor Version 5.00
Method 2: Modify Group Policy settings
(http://support.microsoft.com/kb/320507/ )Internet Explorer does not retry bad proxy server for 30 minutes
Article ID: 271361 - Last Review: August 19, 2011 - Revision: 10.1