I have an old modem I was considering repurposing. The first step I thought to do was connect my computer with the modem and try to map the open ports. I found that, upon connecting the device, that my eth0 interface was assigned an IP address. My computer also has a wireless NIC (wlan0), so I now have two IP addresses. I scanned eth0 and got the results. Then, for good measure, I port mapped my wireless interface only to find that the results were identical. As such, the obvious conclusion is that by scanning eth0 I was in fact scanning myself. So, how can I go about scanning the modem? My knowledge in this space is limited, but in order to do this I imagine the modem itself requires the assignment of an IP. Or am I thinking about this incorrectly? EDIT: The modem is an older Motorola 3360 used ages ago with a DSL connection. 
How to communicate with modem over Ethernet?
ip;modem