I'm doing a preliminary study for a contract to build a VPN network between ~600 remote servers running Linux CentOS 6 (+ their 600 private LANs). The network is supposed to be star-based, so that each remote server connects to a central server(s) to enter the VPN (I know it's a SPOF but that's OK because the main application for which this VPN is built will run on the central server anyway).
I would like to use OpenVPN (it's really flexible and can be tuned to the configuration we need), but I was wondering what are the best practices for running it on such a large network. For instance, if used in tun mode, it would create 600 tun interfaces on the central server(s), which I don't even know if it's supported and/or creates any problem.
I don't have any experience with such a large network, so I'm open to any kind of suggestion and pointers. Thanks!