VPNC - Client for Cisco 3000 VPN Concentrator, IOS and PIX

Vpnc is a VPN client for the Cisco 3000 VPN Concentrator, creating a
IPSec-like connection as a tunneling network device for the local
system. The created connection is presented as a tunneling network
device to the local system. The daemon runs entirely in userspace.

WWW: http://www.unix-ag.uni-kl.de/~massar/vpnc/