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Windows 7: Proxy auto discovery

21 Jan 2010   #1

Windows 7
Proxy auto discovery

I have a linux server with 2 network cards, one connected to the internet and other is internal. The server is running DNS, DHCP for allocating addresses, apache as an internal web server and squid as a proxy so internal machines can browse the internet.

The DHCP server is configured to send option 252 as:

(all domains have been changed to

The DNS server has resolving to the web server.
The web server has both wpad.dat and proxy.pac present and is configured to send them with a content-type of "application/x-ns-proxy-autoconfig"

The problem is that I can not get IE8 on my laptop to automatically pick up and use its proxy configuration. The apache log files show that the laptop is fetching the proxy.pac file but IE8 is not using it.

The really strange thing is that windows update uses the proxy.pac file and can fetch updates from MS (via the squid proxy) without any problems so the proxy.pac is correct.

I know I can manually configure the proxy settings, but I want IE8 to pick them up automatically.

Any ideas on whats going on or how to resolve this?

Here is the contents of proxy.pac:

function FindProxyForURL(url, host) {                                                                       

// If URL has no dots in host name, send traffic direct.
        if (isPlainHostName(host))
                return "DIRECT";

// If specific URL needs to bypass proxy, send traffic direct.
        if (shExpMatch(url,"*"))
                return "DIRECT";

// If IP address is internal or hostname resolves to internal IP, send direct.

        var resolved_ip = dnsResolve(host);

        if (isInNet(resolved_ip, "", "") ||
                isInNet(resolved_ip, "",  "") ||
                isInNet(resolved_ip, "", "") ||
                isInNet(resolved_ip, "", ""))
                return "DIRECT";

// All other traffic uses below proxies, in fail-over order.
        return "PROXY; DIRECT";


My System SpecsSystem Spec


 Proxy auto discovery

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