I'm running a RV320 with WAN1 connected to a ADSL modem and USB1 connected to a 3G backup modem.
The problem I have is that the USB device is configured to stop when the amount of data transferred in the billing cycle reaches 1500000KB, however this setting doesn't seem to be recognised. In the current billing cycle the router reports that total current traffic is 6429945 KB.
I have attached a screenshot of the USB failover tab settings. Is there something I am missing?