For learning about a VPN I'd recommend the wireguard whitepaper. Short and very helpful. Also get your hands dirty and set up a personal VPN. If you just use w

For learning about a VPN I'd recommend the wireguard whitepaper. Short and very helpful. Also get your hands dirty and set up a personal VPN. If you just use wireguard then you have free reign to make any topology you want. And then you get to troubleshoot the routing mess you've made.