I have a U.S. Robotics router, on which there is a DMZ Host configured. DMZ Host's IP is 192.168.1.115, which is the IP of a machine I would like to open to the Internet. This machine is connected to a router through a (separate) switch and has a static IP configured. There are no open ports on the router and this configuration has worked previously.
For some strange reason, it doesn't work right now (after the server and the router have been restarted - I am not aware of any configuration changes in any of thos). When I open the public IP of the router (on both HTTP and SSH ports) I am connected to my router, not to the DMZ host, so I think the problem is related to the router configuration.
The server is a fresh Debian Jessie installation and has connection to the Internet.
How can I diagnoze it?