I think you have something wrong here...
if you ask people what your IP is, they will check their /who(is) reply for instance to see your IP. they will see your outside IP.
if you type //say $ip, you will see the IP mIRC finds (which is your local IP if you change the setting and not have it look it up automatically) and other people will also see that IP as a message in the channel. they however can't lookup your local IP by normal means because only YOUR mIRC knows what that is.
so unless you have a script or whatnot that returns your local IP, other people can't see it.
