using ipfw for NAT mapping in a 1:1 fake:real IPs for VPN

[James Bakner]

Hi,

I have a pretty complicated setup currently and am trying to figure out 
exactly how to implement it.  I'm pretty unfamiliar with freebsd, the 
last incarnation I used was 4.3 and I only used it for a few months 
before moving to linux.

I have a VPN setup for an IP range 10.0.0.1-10.0.0.255 for clients 
connecting using OpenVPN.

Now I am  handling NAT for these up to 5 IPs.  I have 5 real IPs that 
are allocated to the machine that the VPN server runs on (OpenVPN).  I 
need each client to have a real and unique IP, although not from the 
client's viewpoint.

 From my understanding, I would get OpenVPN to give out IPs 
10.0.0.1-10.0.0.5. 

I would then set up rather than a standard NAT for like 192.168.0.0/24 
through A.B.C.D (single real IP)

I would now set up
nat 10.0.0.1 through A.B.C.D
nat 10.0.0.2 through A.B.C.E etc

Does this make sense and am I missing something?  These would be going 
through BSD's tun-type device.

Thanks,

-James