Switch firefox to use a different DNS than what is in the windows.host file

DNS resolving is usually done at the system level and not at the application level, so you can't normally have one program use one dns and another program use a different dns. I'm not aware of any firefox extensions that allow you to use a different dns.

It appears from your question that you already have a second set of DNS servers available that reference the development site instead of the live site.

I would suggest that you simply run a standard SOCKS proxy either on that DNS server system or on a low-end spare system and have that system configured to use the development DNS server. You can then tell Firefox to use that proxy instead of downloading pages directly.

Doing it this way, the actual DNS lookups will be done on the proxy machine and not on the machine that's running the web browser.

What about having different names for your dev and prod servers? That should avoid any confusions and you'd not have to edit the hosts file every time.

I wonder if you could write a custom rule for Fiddler to do what you want? IE uses no proxy, Firefox points to Fiddler, Fiddler uses custom rule to direct requests to the dev server...

http://www.fiddlertool.com/fiddler/

I know this might be not actual but I found solution.

1. Download HandyCache - sorry, don't know English site
2. Just unzip folder anywhere you want
3. Start EXE file
4. Change language to English - looks like Английский (США)enter image description here
5. Go to DNS Cache and (this IMPORTANT) add domain name and IP to resolve. And set up more than 24hours to update records.
6. Then set up firefox to use this proxy HandyCache as 127.0.0.1 port 8080.

Finally HandyCache will return desired IP address for you test domain regardless OS's DNS and its hosts file.

Enjoy!

Since http proxy protocol is similar to raw http protocol, you can redirect desired traffic to your development server by telling firefox it's a proxy server.

keep in mind that this won't let you use https connections.

just copy the following code into a .pac file (enter your site domain and IP address, of course), and switch development/production just by changing proxy configuration.

function FindProxyForURL(url, host) {
    var prox4site = {
        "mysite.com":"PROXY 10.0.1.100:80",
        "www.mysite.com":"PROXY 10.0.1.100:80"
    }

    return prox4site[host] || "DIRECT";
}