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What happens when the hosting web or share is unavailable? IE defaults to no proxy and goes direct(ly past my two proxy servers). I'm trying to make the proxy configuration redundant, so if one server hosting proxy.pac or wpad.pad is unavailable, another server takes its place. Would I need DNS to have two WPAD A Records, pointing to what? Thanks. I'm just trying to eliminate IE's single point of failure.

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3 Answers 3

You should be able to include a failover in the wpad file itself. This is the wpad file we use where I work:

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,"*internal.mydomain.ac.uk*"))                  
        return "DIRECT";

// All other traffic uses below proxies, in fail-over order.
    return "PROXY proxy1.internal.mydomain.ac.uk:8080; PROXY proxy2.internal.mydomain.ac.uk:8080";

}

Does this not work for you?

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That does work, but what we're trying to do is also have the wpad redundant. If IE can't find it (e.g. the server hosting it is down), then it only tries to locate it--it does not read its old version. When it doesn't it find the file, it defaults to direct. We want to prevent that, and have the file exist and be reachable in more than one location, so if one hosting server fails, IE finds it somewhere else. Thanks for your help! –  Network Administrator Nov 10 '10 at 19:56
    
I wonder if I can just set the automatic configuration to point to wpad/wpad.pad and then use DNS to point wpad to two IP locations with A Records internally? –  Network Administrator Nov 10 '10 at 20:10
    
Oh right. I understand now. In that case consider round-robin DNS for the wpad server address as you say... –  RobM Nov 10 '10 at 20:13
    
Thanks. The only downside is having to keep two versions (well, a copy) of the wpad.pad (since one has to exist on both wpad servers). I appreciate your time. –  Network Administrator Nov 10 '10 at 20:25

Would have thought 2 DNS records would work. What proxies are you using? It might be that the proxies can serve the wpad (if they're both down you're boned in any case) and keep things in sync?

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I know this is LONG after the original question, but what about putting your WPAD webservers behind a load balancer?

Otherwise with the two DNS entries, you'll round-robin your DNS and when they pull up the dead one, it's not going to work.

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