I've set up an ikev2 VPN using strongswan on a Ubuntu 18.04 server, and I'm using Windows 10 Pro 1809, and the built-in vpn client.
I can connect to the vpn just fine, and almost all traffic is routed through the vpn. If I visit sites like ipchicken.com or whatismyip.com, they show the vpn ip address.
However, if I attempt to access my reverse proxy, which is hosted on the same server, the traffic comes from my external connection, not the vpn. This means I can't access some services on my reverse proxy that are limited to local ip addresses.
If I access the reverse proxy directly via the server's LAN ip, then the traffic goes through the vpn.