I'm trying to configure a VPN Road Warrior for learning purpose. My VPN Server is my PC at home and I've opened all required ports on my firewalld service and home router. My VPN Client is the Road Warrior and is connected at various Public Wifi Hotspots. The error I am getting on my VPN Server is "022 "vpn01": We cannot identify ourselves with either end of this connection. x.x.x.x or 0.0.0.0 are not usable". The tutorial I'm following is from rackspace (https://community.rackspace.com/products/f/25/t/5059). I have been stuck on this error for a while now and am not able to find any answers via google search. Any help greatly appreciated!!

Don't know that much about VPN's and IPsec, but I have successfully (and hopefully securely) configured L2TP and IPsec in RouterOS in my MikroTik router, so I can connect my laptop or phone to my home network from anywhere. I don't have any idea how to configure L2TP or IPsec on Linux, so I can't really contribute with anything useful there. However, it seems your server sits in your private network behind a NAT router and that could be a big part of the problem. Maybe this could help: https://wiki.gentoo.org/wiki/IPsec_L...ver_behind_NAT
I needed to allow incoming traffic to UDP ports 500, 4500 and 1701 in my firewall to get things to work, but that's with L2TP.

Yes, my server is in my private network behind a NAT router. But I've done all necessary steps to allow it like enabling NAT-T (NAT Traversal) in my configuration and openning all necessary ports 4500, 500, 50, 51.