How To Install Openswan And Create Site-to-Site VPN On CentOS 7

Openswan is an open source, user space IPsec implementation available in Red Hat Enterprise Linux 6/7. It employs the key establishment protocol IKE (Internet Key Exchange) v1 and v2, implemented as a user-level daemon. Openswan interfaces with the Linux kernel using netlink to transfer the encryption keys. Packet encryption and decryption that happen in the Linux kernel.