I set up the built-in racoon program on a Mac server to run a VPN server. It's an L2TP over IPSec VPN. I connect through it through the native client built into macOS's network settings.
So I connect to the VPN and now I can communicate to the server through a separate LAN IP range the VPN works, which is not shared with any other network I ever connect to.
Everything seems to work well. With one catch. On CLIENT machines, websites seem to hang for a bit before they load. Only when I'm connected. It me, it almost feels like the DNS is getting delayed.
I confirmed through www.whatsmyip.org that my web traffic is NOT getting tunneled through the VPN (which is correct), yet somehow its taking several seconds before pages START to load. Then once they start, they load at normal speed. It also won't do this slowdown on the same page twice in a row, which also suggests DNS to me.
Is it possible that just my DNS lookups are going over the VPN? How do you control what connections go over it and which do not? I only know the traditional Mac method, "Service Order" in the Network System Prefs pane. My own ethernet TCPIP settings show my local router as my DNS server, which relays out to either ISP or google DNS servers.