I presently have two routers operating in my small enterprise community setup. One is setup for the principle community and is my Fortinet 80f. It presently has a 1gb circuit from ISP 1. The opposite is a Pfsense sg-3100 which is ready up for our Kraft’s staff solely and it has its personal 1gb circuit from a distinct ISP. My downside is the ISP on my principal router is fairly crappy and has outages on a regular basis. I want to make the most of the 1GB on my 2nd router for failover. I figured there should be a technique to configure the lan port on the pfsense router to have the ability to make the most of the circuit on the principle router. Any concepts on how i ought to proceed with this configuration? vlans, bridge mode,??? assist please!

Network diagram