[CentOS] 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).