Member Avatar for san_fran_crisko

Hi,

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! :)

net_diagram.png 81.44 KB
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Member Avatar for ryan461

I'm not sure why you need NAT for this, you need a router to route between the VLANs. If you can connect the switch to a router, and trunk the VLANs to the router, then tell the router about the various networks on the one interface (sub interfaces) it will route these. A simple linksys wont do this, you need a commercial device.

Member Avatar for san_fran_crisko

I'm not sure why you need NAT for this, you need a router to route between the VLANs. If you can connect the switch to a router, and trunk the VLANs to the router, then tell the router about the various networks on the one interface (sub interfaces) it will route these. A simple linksys wont do this, you need a commercial device.

Thanks for the reply - unfortunately money is tight so I've been told to do this with some old embedded systems kicking around. I'm pretty sure IP Tables will do what I want, it's just finding the time to sit down and work it out.

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