There are two pages in D-Link router to setup access to internal network from outside:
Port Forwarding and
Virtual Server. Both allows to map external port to internal one, except latter page also allows to change port.
I found that if I have service in my internal network and set it up in any of two pages, I can easily access it from outside.
But if it try to access my internal service from inside by external IP address, I succeed only if service is setup by
Virtual Server page.
Is this D-Link bug or that behavior should occur because of Internet protocols? In latter case please provide some explanations.