client ip behind firewall

[sirugo]

I'm trying desperately to grab the clients' ip numbers from behind a firewall, using php.

The webserver is running on a Windows NT, IIS 5.

The http-header "REMOTE_ADDR" contains the proxy-ip only and therefore I try to get the clients' IP-adresses using "HTTP_X_FORWARDED_FOR"-header recommended by various infopages on internet.

When I use phpinfo() to find out at what comes out of each call I see no "HTTP_X_FORWARDED_FOR".

Do I have to activate the use of certain headers such as the "HTTP_X_FORWARDED_FOR" on the server to get the client IP?

Or must it be done at the proxy-server?

 

[jad]

it is usually up to the proxy server ... if it doesn't want to give this to you, then you can't get it.

thought of using cookies in the browser instead?