Help with a iptables script

We have a very small network with looks more or less like this: There's a linux server (let's call it A) that does NAT for the rest of the network. It's also a DHCP server, etc. There's a number of PCs (B1, B2...) that connect to A, get a private IP address from it, and use it to route traffic. There's the ISP router, C, that well, connects A to internet There's a VPN server, D somewhere else in the internet, which also has NAT enabled, so it's possible to access internet crossing it. Server A is also a OpenVPN client, so it has 3 IP addresses: A public internet address that it gets from C, a private IP address that is manually assigned, and a private IP address that it gets from D. So far everything works: From A you can connect to D (you can ping D and use the resources in the VPN), from B you can browse, etc. The job here is to modify our iptables script (nothing fancy) so that traffic from one specific computer B1 is routed to the VPN - so instead of being NAT'ed using A's public IP address it's sent to the VPN. Seems like an easy job for any linux net admin with basic iptables experience. ## Deliverables 1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Employer will receive exclusive and complete copyrights to all work purchased. (No 3rd party components unless all copyright ramifications are explained AND AGREED TO by the employer on the site per the worker's Worker Legal Agreement). ## Platform Linux (Ubuntu Server 9.04 in particular)