Dual DHCP ports for controller

[Mads]

We have embedded a cFP-2220 into an instrument that should have two network interfaces, however both of them *have* to be using dynamic IP addresses, and this is not supported by any of NIs controllers. The secondary port is always static.

Adding a second controlelr just to get two Ethernet interfaces able of running DHCP is not a good solutionI'm thinking that perhaps we could find a router (?) on a tiny board - that could act as a DHCP client in one end, and NAT the traffic to the secondary port of the controller - set with a fixed IP...

(Or we could have only the primary or both ports on the controller connected to this router card. The important things is that from the outside it should look like a device with two different NICs, running DHCP on two different networks...but on the inside it could be just on interface (or two if necessary, but it has to be static IPs on that side anyway then).

Does anyone know of a candidate for such a solution, or have other suggestions on how to solve such a challenge? The "router" should be small(er than the content of a PAC) and energy efficient (more than a PAC which typically uses 3,5-4,5 W).

PS. In reality the devices should only use dynamic addresses when there is a DHCP server available; they need to have a special(!) feature that makes the fall back to the previously received address if the DHCP server is unreachable...but that is a secondary isse. We have been able meet that requirement for the primary port (see discussion here), but with the second port/an external router that will become an issue again....

[Saverio]

Not sure if this fits the bill for you, but maybe a MikroTik RouterBoard might work for you. These things are fully programmable, so you can make it do just about anything you want. Don't know if they fit your size requirement, but the most seem to fit your power requirement. I will give you one warning: learning to configure these things is a steep learning curve.

[asbo]

There's a couple companies that make micro linux boards, where the biggest component is the ethernet port, so it'd definitely meet your size requirement. However, I don't know about the power consumption. Sorry, I don't have any links off-hand.

[Mads]

Thanks for the tips guys. I had looked a bit on the MikroTik solutions already...but we'll see what we'll end up doing. For now I've set up the second port to automatically get reconfigured based on the IP of the primary port. That too took some effort (NIs System Configuration API came to the rescue) and it's not a good replacement for DHCP...but it helps.