Openswan - IPsec implementation for Linux

Openswan is an IPsec implementation for Linux. It has support for most of the extensions (RFC + IETF drafts) related to IPsec, including IKEv2, X.509 Digital Certificates, NAT Traversal, and many others. It has been the de-facto Virtual Private Network software for the Linux community since 2005. If you are running Fedora, Red Hat, Ubuntu, Debian (Wheezy), Gentoo, or many others, it is already included in your distribution.