|If the default address is 192.168.xx.xx then there is certainly and DHCP server involved as well as Network Address Translation as 192.168.xx.xx is a Class C private address.|
What you have a is modem with a built in router, albeit one with only one Ethernet port and one USB port, but a router nevertheless. I had a similar Modem/Router, a Zoom X4, and if wanted to connect more than one computer via Ethernet then I needed a hub or a switch. A modem by itself does not provide DHCP or NAT.
This is were providing the model number of the equipment in question helps as it would make it easier to determine exactly what is happening.