I have a machine with Ubuntu 14.04 that my son set up for me to be a Plex server. It has stopped connecting to the internet or even just the LAN. I verified the switch and cable by swapping in a CAT5 cable from another machine that sits right next to it and is working; no change.
I can see that this machine has a second NIC card port. I have no documentation about the mother board. I need an Ubuntu command to identify the MAC address of the second NIC card; I think when I have that I can set it up with the Network dialog box.