ControlNet and ControlLogix

I have four machines, each machine have 3 chassis's using 1 control logix PLC all connected through controlnet. Is it possible to connect all four machines to the same or different controlnet lines and keep the same i/o addressing on each machine. Do I need to used seperate cards(bridges)?

I don't think that will work on a single ControlNet line. Each ControlNet node has to have a unique address. It sounds like you will have the same addresses used in each machine so you will get address conflicts.
Now, you could install a second ControlNet bridge in each machine and tie all the machines together on that. That would allow the ControlNet acddreses to stay common at each machine.

Keith

Combining three ControlNet segments into one segment is generally discouraged for several reasons:

1. The node numbers are unlikely to be unique. It's very easy to change node numbers on 1756-CNB modules and in RSLogix 5000, but it will require some reprogramming.

2. Network bandwidth. A four-node network is a no-brainer for bandwidth, but a twelve-node network might require a little evaluation of the scheduled data bandwidth available to each ControlLogix.

3. Schedule dependency. Because all three systems will be on the same ControlNet scheduled network segment, you will need to take all three ControlLogix CPU's into PROG mode to make a schedule change to one of them.

You'll also have to consider the trunk length equation of these controllers are a long distance apart.

Given the choice, I'd add a 1756-CNB or 1756-ENBT to each CPU chassis and interconnect the systems with a separate ControlNet or EtherNet/IP link.