secure-tunneling strongSwan is an OpenSource IPsec implementation for the Linux operating system. It is based on the discontinued FreeS/WAN project and the X.509 patch which we developed over the last three years. In order to have a stable IPsec platform to base our future extensions of the X.509 capability on, we decided to lauch the strongSwan project. Enable support of Cisco VPN client Enable NAT traversal with IPsec transport mode