Network Shares Over Internet

Not sure if this is the right forum or not, but here it goes.

Last night i discovered something, i'm not sure why it's working, but it does..

I have a network setup in my dorm. I have a server computer, basically it looks like this


SERVER ----> Internet (straight to it, no firewall, anything)
|
-----> LAN (static IP address setup) ---> Printer, Laptops, etc


The server has two NIC cards, one that connects to the internet, one that connects to the LAN, now ICS is enabled, the LAN cannot see the internet.

Ok, if i connect my laptop to the LAN, and map a network drive to the server, then disconnect from the network entirely, go to a different building, completely different ip address as the server's external, and go to my computer, i can type in "\\xxx.xxx.xxx.xxx" hit enter, and all of the network shares from the server show up.. I'm in Ohio, and i've gone back to Indiana and connected in this fashion...

I can also print to the printer from anywhere using the external ip address of the server.

should this be able to happen? I have also found that if you have not mapped a network drive from the LAN (internal static IP assignment) you cannot accomplish this..

Thanks for your help, i hope the picture assists