• System Preferences > Network
• Click '+'
• Interface: VPN
• VPN Type: L2TP over IPSec
• Server address: Your instance's public IP address or DNS name
• Enter your Foxpass username in the "Account Name" section
• Click Authentication Settings
  • Password: your password
  • Shared Secret: the PSK configured when setting up the VPN
• Click Advanced
  • Tick "Send all traffic over VPN connection" (Note: this may not be needed in recent macOS versions)

Two choices:

(In the example below, replace 172.30 with your VPC's prefix, and 10.11.12 with your VPN's IP block)

1. Each time you connect, type

sudo route add -net 172.30 10.11.12.1

2. This is an alternate method that sticks, and will work beyond client stops, and restarts and reboots.

Get the name of your VPN entry in networking

› networksetup -listallnetworkservices
...
vpn-us-east-1
...

› networksetup -getinfo "vpn-us-east-1"
IPv6: Automatic
IPv6 IP address: none
IPv6 Router: none

sudo networksetup -setadditionalroutes "vpn-us-east-1" 172.30.0.0 255.255.0.0 10.11.12.1