I followed this approach to solve a similar problem to that posed by the OP (dev wanting to refresh on TCP/IP and networking for k8s) and I can confirm it works

I followed this approach to solve a similar problem to that posed by the OP (dev wanting to refresh on TCP/IP and networking for k8s) and I can confirm it works. I got some second-hand gear which was useful because they didn't have any niceties, but basic Ubiquiti kit will blow away consumer-grade kit. Setting up some WireGuard VPNs is pretty useful and easy to practice with too. I wanted to replace my existing gear, so I didn't choose to go with pfSense. If you have some free computers that can accept additional network cards, then that might be a good outlet. People were pretty enthusiastic about it. People on the reddit.com/r/homelab and WillieHowe.com Discord channels were pretty friendly when I had questions. TCP/IP Illustrated is a really good book for a developer to have. It might not be as useful for someone without a dev background.