If you are NATed it's hard to reach Endian directly. All options will lie on having some external server with a fixed IP.
http://davidhsiehlo.com/bypassing-a-nat-slash-firewall-by-reverse-ssh-tunneling/ When we had this problem we just simply install some remote access app on a windows machine behind the firewall (like Teamviewer), and access from it.
It's far from ideal, but as we have the Windows machine this was the simpler setup, no own external VPS server to reverse the access.