To setup Simplifi Failover using a existing modem /router combination, simply connect a LAN cord from your existing Modem/Router output into Simplifi using the USB to Ethernet Dongle then plug the USB end of the dongle into Simplifi. No additional configuration is necessary. Plug a LAN cord from the port on Simplifi to your LAN connected devices. You may need to purchase a separate switch for this to happen depending on how many connected devices you have.
In this configuration, your existing ISP (Internet Service Provider) will provide primary Internet through Simplifi where Simplifi will then pass this data through to your devices via LAN or WiFi Should your primary internet go down, Simplifi will automatically continue providing Internet using its cellular internet as the failover to your Router and switch.
In this instance, it is best to configure your WiFi Devices to the Simplifi SSID, however keep in mind, that there will minimal data charges as your primary ISP will be providing the data. Your cellular data will get used when the mainline ISP goes down.
For more information, please go to https://www.simplifi.io/failover for additional details