EDIT: I know how to use NAT, I specifically want the server to be reachable on two IP's, one private, one public, with the firewall of the OpenWRT in between, if feasible.

At the office we have recieved a /29 from our ISP. The first address is reserved for their endpoint, so I'm free to use five addresses.

We run a local network, so of course there is a router in between running OpenWRT to provide all hosts with (W)LAN (dhcp from a private range).

However, we also have a server running OS X Server 10.6 (Snow Leopard) and I'd like that server to be accessible both from the LAN using a private IP as well as from the WAN on it's own public IP.

Point of note is that the server only has one network port, so multiple NICs is not an option, unfortunately.

How would I go about doing this?