[ubuntu] Ethernet cable coected but not working - Ubuntu 16.04 LTE

Perhaps you have a known bug in ubuntu 16.04 with wired net.

You can edit the file /etc/network/interfaces ( use gksudo gedit /etc/network/interfaces ), and see that you have commented with # sign at the begining two of the lines, as it is shown below :

#iface eth0 inet dhcp

#auto eth0

So, your interfaces file will show as :

auto lo
iface lo inet loopback


#iface eth0 inet dhcp

#auto eth0