Linux FreeS/WAN
An implementation of IPSEC & IKE for Linux: http://www.freeswan.org
Is no longer in active development, but there is an active fork at: http://www.openswan.org/
- Via some AES patches, it possible to set up a VPN using a very wide set of authentication and encryption algorithms.
See also
VPN,
Linux,
PPTP, or
Networking