CentOS - Feb 2018 - In reply to: What is best way of managing isolated network environment?

(Couldn't find the original request in my email but definitely have an
idea).

Set up an OpenVPN server on your network and create a client on the isolated
network (set up to connect on boot), configure routing appropriately. You get to
decide what subnet the VPN IP address is on, in this situation I recommend a
static IP address for the client. From your network you connect to the OpenVPN
IP address and connect to the rest of the isolated network from it (or set up
multiple clients on the isolated network).