Type /sbin/ifconfig at shell prompt then press Enter button. Note: If you see an error message to the effect of "permission denied", then instead enter su -c "/sbin/ifconfig" at the shell prompt, and enter the password for the "root" user if asked for it.
Details are shown for each of the computer’s network adapters. Usually, Ethernet connection is identified with eth0 label. The MAC Address is in the HWaddr field.