Port 16 (uplink)

Here is my dumb question of the day, which is not a good day today to this point.

Is port 16, which is next to the uplink port on my swtichbox, not used as a regular port.

Today I plugged in a cable in port 16, and we lost connectivity to the internet (we use asdl line).

Just curious if that was a well known thing.

Thanks,

Bill