Could you please look at the attached network example of a OEM and give me a summary

Good Evening ,

Attached is a network drawing of a CompactLogix PLC with a CPU and a ENBT bridge module. It seems kind of unusual to me . We, as the customer will provide 2 IP Addresses to the ENBT , that will be totally different from the overall machine. The machine manufacture will use a block of about 16 IP Addresses from a Network Card , in the CPU . These IP Addresses from the Network Card will then communicate with the machines Kinetix Servo Drives , PowerFlex 525's , Flex I/O , etc. What possible Network Card would be in the CPU ?

We want to give the OEM an entrance into the machine remotely. Not sure this is the reason or not. I need to research the prints a little more. I was just briefed on this portion late this week.

Thanks so much for your help.

They're mixing models of network cards, so I'd ask for clarification on what they expect.

The sketch appears to show a network port on the CPU itself. That would be consistent with a modern CompactLogix, or with a 1756-L8x ControlLogix. Both have an EtherNet/IP port on the CPU module itself.

A 1756-L8x controller could be used with an older 1756-ENBT in the same chassis. That might be existing; the 1756-ENBT is the 2nd generation Ethernet module and has been largely supplanted by the 1756-EN2T and -EN3T high capacity modules.

And the label of the PLC bus being "Rockwell" and "No EtherNet/IP" seems weird.


In general, you can put multiple Ethernet modules in a ControlLogix backplane and connection one to I/O devices and another to the HMI or enterprise network. That's a good way to segregate I/O traffic from the enterprise network and infrastructure, and the Rockwell software tools can still cross the ControlLogix backplane.

But only one obsolete generation of CompactLogix (the 1756-L43 and -L45) ever supported multiple Ethernet modules.

Another method that works well with CompactLogix is to put a Network Address Translation (NAT) device on the network, to allow an enterprise network IP that's mapped to the controller (and other devices) in the automation network. Rockwell makes a couple, and industrial routers and security appliances are becoming more common.

Thanks Mr. Roach . I'm not yet familiar with the 1756-L8x or the L7x . I do need to replace a L62 with a L72 in another machine , that I need to replace , that I hope goes well.

Thanks again , Sir

I would put everything relating to the machine off the ENBT, and reserve the CPU onboard port for pc / remote access. Keep it all separate.