Using Simplifi with a Firewall is used on most enterprise or Small Business applications. This will require the knowledge your Network or IT professional and familiarity of your firewall device.
While we can’t comment on all application, the typical installation would be to connect Simplifi to your Firewall using a LAN cable from Simplifi into a secondary WAN port of the firewall. Configuration of this firewall will occur allowing all traffic from this same port to continue only if the primary port goes down.