If your switch supports vlans, you can use just about any cheap computer (ARM SBC, or some old desktop off of ebay) as a firewall+router combo. That is, on the

If your switch supports vlans, you can use just about any cheap computer (ARM SBC, or some old desktop off of ebay) as a firewall+router combo. That is, on the switch plug the internet modem into vlan A (access), assign LAN ports to vlan B (access), and use the last port to trunk vlans A & B to the cheap computer. From there, you can use vanilla linux or BSD to firewall & route between the two vlans. Only suggesting this because finding something cheap with more than one NIC is a tall order. Best practices, no. Cheap, yes. If you can get a super-cheap PC, decent gbit nics can be found for under $15, and that would eliminate the vlan nonsense.