I would like to install a vpn on a droplet and connect it to an AT&T private network with the 172.16.x.x ip range and then have other droplets route traffic to the vpn droplet. I know you can usually put this "up route add -net 172.16.0.0 netmask 255.240.0.0 gw 10.x.x.x" in an ubuntu /etc/network/interfaces and have it route traffic to that server which then because of the VPN would send it to the AT&T private network. I have read a lot of things that make me believe this may not be allowed on your private net.