A customer requires us to connect to their system via a site-to-site VPN tunnel. ("Client-based VPN solutions are not accepted.") Once the tunnel is established we'll be consuming data over the connection via a JMS API.
Here's the catch: We'd like to establish this VPN tunnel from an external-facing Ubuntu 14.04 LTS server with one NIC. Because this server is essentially standalone at a third-party data center, it has no LAN/subnet configured, and no hardware router/firewall under our control.
How can we do this? Our plans are to use OpenSwan or similar. Can we configure a LAN on this single server and associate an internal IP address with the server, and then configure the VPN tunnel accordingly?