We have 3 LANs in different locations wanting to be connected into a WAN via OpenVPN. Connecting them through Cisco routers isn't an option because on 2 of the LANs we have NO control over the networking equipment(Let's call that site the Site B & C), i.e. we can't open ports on them or configure any routings.
This leave our only choice on OpenVPN. We would like to host our OpenVPN server(windows based) in Site A and have the site B & C to connect to A as clients. All the hosts in Site A, B & C can ping each other without having openVPN client installed individually except the 3 computers that act as Server and Clients at Site A, B & C respectively.
My question is, is it even technically possible to implement such thing under the above-mentioned constraints? If so then what would the configurations be like?
As of this point, I am able to configure a host-to-site a.k.a. RoadWarrior configuration that allows clients(but not hosts that doesnt have openVPN clients configured) on B & C to ping all the hosts on A, but not vice versa. Thank you in advance to all the experts for any input.