I'm trying to use either one or two old embedded x86 devices to build a NAT server, however many it takes. It's a bit unique in the sense that I need full transparency (i.e. no firewall) and fully duplex NAT. I have a network switch which is separated in to separate VLANs. There are devices on each of these VLANs with unique addresses - e.g. VLAN 1 = 172.16.1.1-254, VLAN 2 = 172.16.2.1-254 etc... I've attached a crude network diagram to help show the setup.
At some point the devices on two separate VLANs will need to be able to talk to each other, hence the requirement for some form of NAT. I've been looking round various Linux distros to utilize iptables and it may be able to do what I'm looking to do, ideally with webmin sitting on top to make everything nice and easy to use :).
I've also tried using m0n0wall as it appears to offer everything I need but in hindsight it doesn't.
I suppose to sum it up, I need a multiple IP <--> multiple IP NAT server. Although all LANs will be separate, their address range is 172.16.0.0/16 (255.255.0.0) so if they were all on the same LAN they'd be able to talk to each other (if I'm not mistaken!). I just need to put a degree of separation between the LANs so the hosts on each cannot talk to each other until they get to the final host at the end of the traffic chain which faces the NAT server.
Thanks for your time! :)