What is the USB port for on the back of the C1900A

The USB port is currently not activated on the C1900A as January 2018. When CenturyLink activates it, you will be able to use it for attaching a network storage device directly to the C1900A. Actiontec does not know when that will be. If you are looking for more information please contact CenturyLink Techincal support at 1-877-348-9005