Why does the user's IP is a local one when accessing the page using the global URL?

I am logging every user's IP when they access the company's page.

There are two ways to access the page from inside the local network:

http://company/webpage

and

http://ift.tt/1ooAwgh

What bugs me is that even when the users use the https global IP, their accesses are still recorded on database with their IP as 10.50.1.12 or 10.50.1.100.

Does that means that the browser or something else is redirecting the http://ift.tt/1ooAwgh to company/webpage? Or does that mean that I'm using a flawed method to log the users IP?

Another way to ask my question (just to make sure I'm being clear): if I'm accessing my Internet web page from inside the LAN network, am I effectively going outside my network and then back? If not, where am I going wrong with my logging?

Code used to log user's IP:

user.LastIP = HttpContext.Current.Request.UserHostAddress;

I'm curious about this because I want to make sure the users inside the company will access the page using exclusively the LAN Network. The goal is to save bandwidth usage, which is scarce.