Linux firewall + NAT Traversal + IPsec

[John Mok <jmok@xxxxxxxxxxxxx>]

Hi,

I'm new to Linux. Is it possible make a Linux box with firewall + NAT, 
such that client PC(s) from the NATed internal network could connect to 
a VPN gateway on the Internet :-

client PC ----- Linux iptables firewall + NAT ---- Internet ---- IPsec 
VPN gateway
192.168.x.x/16                                              (e.g. 
Checkpoint FW-1)
(VPN client)

I hope someone could help to advise what software / kernel patch is 
required on the Linux box to NAT traversal work and where to get the 
HOWTO(s)?

Thanks a lot.

John Mok