Use pfSense to set IPSec VPN

CUHK
setting client
http://www.cuhk.edu.hk/itsc/chinese/network/vpn/cwinxp.html
setting host
http://www.cuhk.edu.hk/itsc/network/vpn/fedora.html

MONO howto.
http://doc.m0n0.ch/handbook/ipsec-tunnels.html
pfsense howto.
http://doc.pfsense.org/index.php/VPN_Capability_IPSec