Back with web developer guy wearing net admin hat. Hopefully this is an easy one.

We have two servers on a public network at a hosted facility. Server A is our public-facing web server and server B is our database server. Both are running Windows 2008 Server R2 Web Edition. We want Server B isolated from everything except Server A, such that anyone who has to connect to server B goes through the VPN on Server A. It's not perfect since we have no access to do this on the router side, but it's what we've got.

We've set up VirtualBox and OpenVPN Access Server on Server A. It has one network interface set to 'NAT' mode, such that OpenVPN gets its IP at 10.0.2.x, and to connect to the OpenVPN interface, I go to the local IP for the Virtualbox network adapter, 192.168.56.x, which works as I configured the appropriate ports using VBoxManage.

My question is, do I need to be using Bridged Networking and give the VPN server its own IP, or is there some way to tell the server (either Windows or the Virtualbox OpenVPN) that 'any public connection on the real external IP on port X should be directed to this internal LAN address of 192.168.1.x on port Y'? OpenVPN itself doesn't seem to be aware of the server's real external IP unless we put it in Bridged networking mode; is that necessary or advisable?

We're without RRAS since this is Web edition, but I feel like what we're going for is pretty simple.

Thanks! Aq