What "router" do you have from your isp. Do you also modem? Or do you have a gateway modem/router combo.
Pfsense meant to replace your router so it gets a public IP on its wan interface, and then you have your lan segment(s)
Typical setup could be something like this - see attached
Now you could have your lan side segments vlans all through the same switch or if you have physical like shown with say 4 nics total, you have 1 for wan, then 1 for your lan - then I would break out wifi on its own, and then you have another segment where you put stuff that you forward traffic too. So this is pretty much isolated in its own dmz if you will.
What switch(es) are we dealing with? Why type of appliance are you looking at for pfsense - how many nics? I personally would make sure it has 4. 3 you could get by with, well 2 even but 4 is the sweet spot if you ask me this allows to do full physical connections at full gig speeds with our having to vlan and hairpin interfaces, etc.
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