How to 'snoop' a wired connection?

In the 'good old days' you could run 'snoop' on a wired network connection and see the packets going by. (Before the days of switches.)

I have a router that disconnected from anything other than my Ubuntu laptop. I have no idea what network it is set to use, and just broadcast pinging obvious possibilities gives me nothing.

The tools that exist seem to only work on WiFi interfaces not hardwired.

Ideas please.

David

Solution 1:

what I usually do when I find a lost device is connecting to it with my computer and setting tcpdump to listen to that wired interface:

ES: tcpdump -i eth0

in this way you might see some packets from the device and find it's ip. I've used this workaround many times.

edit: in this case I'm using linux as my OS and have to launch the command with elevated privileges, thus with "sudo" infront or from the root user.