Loss of guest connectivity after connecting VPN on host

[rzzldzzl]

I spent hours figuring this out and wanted to share in hopes it helps others...

Your VPN might disable IP Forwarding. That is the case with the AWS Client VPN.

IP forwarding is currently disabled when using the AWS Client VPN Desktop Application.

My experience with Network Mode Shared Networking:
The guest can access networks as expected (IP Forwarding is enabled)
After the host connects to the AWS Client VPN, the guest looses access to anything but the host. (IP Forwarding is disabled)
Manually enabling IP Forwarding restores connectivity from the guest.

After connecting your VPN (on the host), try enabling IP Forwarding on the host:

% sudo sysctl -w net.inet.ip.forwarding=1
net.inet.ip.forwarding: 0 -> 1