USB modem not selectable as outgoing VPN WAN
I was planning to use ER605 routers for VPN tunnel connection between branch offices and main office.
The configuration would be to use the main fiber optic gigabit link for primary WAN and a 4G USB modem as backup link.
This turns out to be impossible since the USB modem cannot be selected as WAN link in VPN configuration.
When using an external 4G modem with ethernet connection and configuring the ER605 with 3 WAN ports, it's working fine when connecting fiber link to WAN and 4G modem with ethernet port to WAN/LAN port (port 2).