Remote access VPN with Ipsec StrongSwan

StrongSwan is a VPN (Virtual Private Network) implementation based on IPsec, open source, multiplatform, complete and widely used. It works on operating systems such as Linux, FreeBSD, OS X, Windows, Android and iOS. Mainly, it is a key exchange demon that supports Internet Key Exchange protocols (IKEv1 and IKEv2) to establish security associations (SA) between two pairs. [NOTE] I will start from the VPN post remote access with OpenVPN, so you may refer to this during this article. If you want to have the same scenario go first to this.