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msmiha

EthernetIP problem with big number of PLCs

14 posts in this topic

Hi everyone! I have a problem with Omron PLCs CJ2M-CPU31, communicating to a SCADA CX-Supervisor v3.1 over EthernetIP. Actually I got 27 same PLCs connected to the EthernetIP network. The problem is that communication is working fine with 4-5 PLCs and sometimes even if I add 6 or 7 to the CX-Supervisor project. But when I add more and more PLCs, network becomes more and more overloaded (at least that’s what CX-Supervisor says). The response of SCADA is getting slow and it looks like it hangs. Now if I try to communicate with CX-Programmer the same time my SCADA is ruining slow, I can’t make a connection to the PLC or the connection is working really slowly. Has anyone ever had problems like me with Omron PLCs? Why does the communication start to run slowly? I’ve done some analyses with wireshark but the network is not nearly overloaded? There is no duplicated IP on the network. The PLCs are connected to the 8 port switches and those switches are then connected together (star and tree connection). Can anyone help please?

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Try using a different port number for each PLC. (PLC1: UDP 9601, PLC2: UDP 9602, etc.).

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Currently I'm using EthernetIP connection so a default port is 44818. I can try to use normal Ethernet FINS/TCP or Ethernet UDP and then try to change ports. I will then report the results

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My local Omron Guru always recommends UDP as he reckons it is far more efficient. I take his advice - give it a try.

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Even on UDP, I found that CX-Server comms is not really efficient on multiple Ethernet hosts. Lately i have been bypassing CX-Server and using FINS gateway which seems to have improved performance.

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Hi No CX-Server is not efficint had the same problem, my project is with 2 PLC (CJ2), 2 HMI(NS15) and 2 PC ( CX-supervisor 3.1). I got better comms performens by Setting the 2 plc,s on fixed scantime and incresed the peripheral service ( Set time to all events ) Banker

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Hi Banker, Would you mind posting some screenshots of your settings? Always interested in altenative setups...

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Are you using a managed or unmanaged switch?

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I've also been in contact with Omron and they are assuming that problem is with the switches. I'm using unmanaged types. Now we will replace them with managed type, and see if there will be any differences. Has anyone else got any experiences with switches? Which one do you prefer?

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I normally use the Omron ones but I am not sure if they are managed or not. They are 24VDC powered and work fine for me but have not tried with that number of PLCs.

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While I have no experience with Omron PLC's, I did have a similar problem with an Allen-Bradley PLC system where I had multiple PLCs and HMIs on a system. As soon as I put the PLC behind a managed switch, my problems disappeared. One of the things a managed switch does is to manage the traffic (what a surprise, right?). This means that it knows what device (or devices) live on what ports and any traffic it sees coming in is only forwarded on to the proper port or that traffic is ignored. This, in turn, keeps the processor from having to look at, analyze, and ignore messages that are not meant for it. Now, anytime I design an Ethernet based system, I make sure to use at least one managed switch in the system. This allows me to interconnect multiple PLCs without having to worry about bogging down it or any other PLC with unnecessary traffic. Steve

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Ethernet/IP generates high levels of multicast traffic. It is best to use a switch suitable for Ethernet/IP a switch that supports: IGMP snooping port mirroring and full-duplex switching

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Just as an informational note, Allen-Bradley has recently started allowing you to use uni-cast instead of just multicast traffic. Steve

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Steve, Thanks for the info, I've just recently started switching projects over to omron when i can. Omron have the option for unicast or multicast, but it defaults to multicast. I would assume that if the original poster has the plc's connected in star/tree configuration that there would be quite a bit of traffic up the trunk lines between switches.

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