Proxy failure detection RRS feed

  • Question

  • Hi Team,

    I need to understand how IE detect primary proxy failure and fail over to secondary proxy defined in PAC file?

    Is it based on internal IP (Network layer) reachability or external website reachability (Application layer)?



    Wednesday, February 1, 2017 9:23 PM

All replies

  • Hi,

    These articles can give you some ideas, please refer to the links below:

    Over the last decade, I’ve come to learn a lot about web proxies, having chosen to implement my web debugger as a proxy. In today’s post, I’ll provide an overview of proxy-related information,
    including information on changes in Internet Explorer 11 / Windows 8.1.

    Understanding Web Proxy Configuration


    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:

    How to disable automatic proxy caching in Internet Explorer


    Hope it can be helpful to you.

    Best Regards,


    Please remember to mark the replies as answers if they help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    • Edited by Tony_Tao Tuesday, February 14, 2017 6:57 AM
    Thursday, February 2, 2017 4:14 AM