To show connection info about all NICs, use ifconfig. However, it will show all the interfaces connection info, including loop back, virtual interfaces if you install VMware or VirtualBox.
To show only information about a interface(en0):
ifconfig | grep -A 4 en0
grep is a unix command, you can find it in the linux section.
-A means how many lines after the matching line. Here is 4 lines, because in MAC there are 4 lines for each NIC.