Connection information not available

I am trying to get the IP address of my modem/router. I plug a LAN cable into it and into my PC, but the GUI Connection information is grayed. If I try the Terminal's IP route nothing happens. Does it mean that connection was not established and there is something wrong with the modem/router, or is it a SW problem?

Usually, you reboot your pc after you connected a cable.
The modem should provide its ip to your pc.
if you want to know your public up,

I wont to know the modem's IP, to log into its settings via the Internet browser.

that would be (cable modems here in the US)

I performed a modem/router hard reset and it works.