Back in 2015, I ran a FreeBSD router on my Rasberry Pi 2B. Instead of relying on two ports, I divided a single port using VLANs, and connected my modem to a L2 managed switch. This configuration is colloquially known as "router on a stick." Performance wasn't amazing, but neither was my rual ISP, so I ran with it for a year. I eventually replaced it with a Beaglebone setup in the same configuration, but with OpenBSD, and an IPSec VPN. That setup remained until I moved out a couple years later. I have been wanting to try it again with a PoE-capable RPi - removing a dedicated power cable and only requiring a single cable would truly make it a "router on a stick."