iptables
These slides give a brief introduction to how to set up the VPN-like network between several clusters which connect to each other through Internet:
vpn_iptables_v2.pdf
Animation is enabled which may help to ... read more »
Sharing the networking is important. Setting up a gateway is a good solution to it. Building up the gateway on a Linux box is easy and cost efficient, but reliable. ... read more »
Port forwarding is simple to do with iptables in a Linux box which may probably already being used as the firewall or part of the gateway operatioin. In Linux kernels, ... read more »