automatically configurate proxy on browser using proxy.pac

*** setup information ***
- apache2 server (http server) ip address: 192.168.202.1
- proxy server ip address 192.168.202.25 port 3128

1- setup apache2 server to serve proxy.pac file
$ sudo apt-get install apache2

2- normally apache2 root directory is /var/www/html, so can create file /var/www/html/proxy.pac with the following content

function FindProxyForURL(url, host)
{
    return "PROXY 192.168.202.25:3128";
}




- our proxy ip address 192.168.202.25 and use port 3128,

3-  then on browser you can choose "use automatic configuration script" and type the url http://192.168.202.1/proxy.pac

the configuration should look like below

4- how when we use the browser with about configuration will use proxy 192.168.202.25 to internet

5- so if you have two of more proxy and want some subnet to use other proxy you can update the proxy.pac as below

function FindProxyForURL(url, host)
{

    if (isInNet(host, "172.16.0.0", "255.255.254.0"))
    {
        return "PROXY 172.16.1.254:8080";
    }

    return "PROXY 192.168.202.25:3128";
}

- with configuration above if the client is in network 172.16.0.0/23, it will use proxy 172.16.1.254 port 8080 to go to internet.