The Proroute H685 WRT 3G/4G Router is supplied with 1 x rJ45 Ethernet LAN port and 1 x RJ45 Ethernet WAN Port.
If you don’t need to use the WAN Port for failover configuration, but need an extra LAN port then you can quickly and simply change the WAN port into a second LAN port.
Here is the video that shows you how to do it
Just remember to reboot the router after you made the change.