I've actually used http://www.tinc-vpn.org/ http://www.tinc-vpn.org/ to tunnel Tokyo Tyrant between data centers. It was a bit flaky at times though, so hardwar

I've actually used http://www.tinc-vpn.org/ http://www.tinc-vpn.org/ to tunnel Tokyo Tyrant between data centers. It was a bit flaky at times though, so hardware Cisco tunneling looks like a good option if you have access to the firewall in your environment (eliminates all cloud providers).