Hi!
You seem a little confused about networks, am I right?
The thing is that to configure your cFP, it must reside on the same subnet as your PC. I make an example: you can assign your PC a static IP address, example 192.168.168.1, subnet mask 255.255.255.0, then your cFP-2120 will have to be inside this subnet, that is 192.168.168.2 to 192.168.168.254. If you connect your PC to cFP-2120 through a cross ethernet cable, you can set your PC IP address to 192.168.168.1 and cFP-2120 to 192.168.168.2. With this gear, you configure, program, and test your cFP application.
If I understood your needs, you need to place the cFP-2120 remotely, and collect data over Internet, isn't that? If so, one way for doing this is activating a web server on the cFP-2120, for which you can find examples.
The next step is to be able to view your cFP-2120 remotely, because of course you can't keep IP addresses you used for configuring cFP-2120. When placed remotely, cFP-2120 will reside on a different LAN, I suppose, and you need to access it from your PC. Unfortunately, I have no experience on this, but I think that once you configure cFP-2120, create application, create the web server, then you can turn to remoting cFP-2120.
Some useful application notes are
here, in particular take a look at links at the bottom of the page.
Hope this helps!
graziano