FreeBSD Firewall + NAT Traversal + IPsec

[John Mok]

Hi,

I'm new to FreeBSD. Is it possible make a FreeBSD 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 ----- FreeBSD 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 is required on the 
FreeBSD box to NAT traversal work and where to get the HOWTO(s)?

Thanks a lot.

John Mok