I have a computer on a small network, so my ip is 192.168.2.100.
I am trying to get my real ip. I download the no-ip client but that just seems like a lot of trouble
The way you're doing it is probably as good as any.
You say you have a public FTP site -- do you also have a web site there? Your other option is to have your local machine access a php page on that public facing site. That php page can verify it's you and then use the $_SERVER['REMOTE_ADDR'] to record your external IP.