While VPN client machines can ping inside of the advertised networks, you might've noticed you cannot ping those same VPN clients from inside of the network not matter what you do. The only machine which can ping those VPN clients inside your network is the VPN server/gateway.
I found a way to backup machines online using this trick. Make a virtual adapter in eBox on your VPN server machine. Then go to the firewall and forward all requests on that IP to the VPN client's IP. Now you can backup machines over a VPN. Another method is just forwarding a specific port or set of ports.
Topic: Backup VPN'd machines using BackupPC (Read 2298 times)