We need to run ifconfig and look for the status line.
Remember this about ifconfig output:
* if “status: active“, the port is linked up and sending traffic (now you just need to make sure it has an IP for it to be able to communicate on a network). You can see it is sending traffic with tcpdump -i <port>
(hit Control-C after a few seconds; even ports that are linked up w/ a missing IP should still be sending out and receiving some L2 switch traffic: STP, ARP, LLDP)
* if “status: no carrier“, the port is not linked up and therefore not sending traffic . If you run tcpdump on this port, you will see 0 packets.
* if “status:” line is missing, then the port is disabled. Enable it w/ “ifconfig <port> up” to see if it has a link (you can optionally disable the port afterwards if you see it has no carrier using “ifconfig <port> down“)