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Old June 19th, 2009, 10:18 AM   #1
MCB
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Eaton SVX9000 VFDs and RSLinx Ethernet/IP Issues

I recently made a post about a customer's job site that supposedly RSLinx Ethernet/IP would fault the PLCs as stated by the customer. After making a return visit this week to actually test the PLCs, I found the actual problems. The PLCs never faulted. They continue to run just fine.

They have Eaton Cutler Hammer SVX9000 VFDs with an Eaton Multiprotocol Ethernet Module part number OptCI.

There are 3 PLCs in the plant. Each PLC cabinet has a PanelView Plus display. And up in the one building is a PC running RSView that enables you to see the entire plant. This PC is where my problems are at:

RSView works perfectly and the plant runs just fine... In RSLinx, it is configured to use the Ethernet/IP driver.

The problem arises when they want to add tags to the PLC programs from that computer, or say they open RSLinx and expand the tree on that of the Ethernet/IP driver. As soon as you do that, all 3 VFDs lose communication with the PLCs, and all of the alarms go off on the system.

The only way to recover from that is to power cycle the drives (they lock on their current speed, but will not communicate with the PLCs.) But this is a separate issue.

So anytime RSWho tries to browse that subnet in Ethernet/IP and find all of the devices on it, the VFDs lose communication.

Now, if I just use the plain Ethernet driver, and enter all of the IP addresses that way, there is no problem. It does not cause the VFDs to go offline.





I am just trying to find a solution here as to why the Ethernet/IP driver is causing this problem.
If I cannot find a solution there, I can go with just the Ethernet driver, but then RSView will have to be reconfigured to do so.

Last edited by MCB; June 19th, 2009 at 10:22 AM.
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Old June 19th, 2009, 12:09 PM   #2
Ken Roach
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Thanks for posting this follow-up. What a very strange behavior.

The RSLinx Classic "EtherNet/IP" driver discovers devices on its subnet by issuing a broadcast packet with the CIP command "List Identity" in it. Every device on the network responds back with its identity information, which is what makes up the graphical view of the RSWho window.

My initial hypothesis is that the C-H drives break their connection when they get a List Identity request, or that they break their connection when they see a broadcast packet.

A secondary hypothesis is that when all the drives and devices respond to the RSWho broadcast at once, it pushes the drives over a precarious ledge of traffic handling capability. That would allow for these drives working fine at the factory but failing in your installation.

Neither of these hypotheses accounts for the drives faulting when you create a tag in a controller. That should have absolutely no effect on the I/O connection of the drives.

Can you describe the Ethernet switches that are used in this system ? Is the RSView computer on the local IP subnet, or across a router from the drive network ?

Are you familiar with using port mirroring and Wireshark or Frontline Test Equipment's NetDecoder software to capture Ethernet traffic ? I'm certainly curious, and I'll bet Cutler-Hammer would be too, about exactly what the Ethernet traffic is like at the switch ports to which those drives connect.
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Old June 19th, 2009, 12:59 PM   #3
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Hi Ken,

There are 3 Dell PowerConnect 3424 switches on the network.

The RSView computer is on the same local IP subnet, and there are no routers on the network.

The Dell switches I had to configure while I was there, as they appear to have been running with the default settings all this time. I thought I had set them up correctly, but I did not set up Port Mirroring.




This is my first time I have ever configured a managed switch, and I might just need pointed in the right direction.
I have attached a picture of the Port Mirroring screen on the Dell Switch.

The customer just sent me a file that an engineer from Cutler Hammer had created from a previous site visit about the Packet Tracing on the network. I was not aware this had been done already.... But he never configured the switches either...



Thanks again,

Mike B.
Attached Images
File Type: jpg CarrierUG_A01.jpg (23.7 KB, 23 views)
File Type: jpg packet trace 1.jpg (98.1 KB, 25 views)
File Type: jpg packet trace 2.jpg (124.5 KB, 21 views)
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Old June 21st, 2009, 02:27 AM   #4
Ken Roach
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These "packet traces" appear to be captures of IP traffic done by Wireshark software. If you have the *.CAP or *.PCAP files themselves, those would be even more helpful.

The "packet trace 2" file is the most informative.

Because it shows I/O data addressed to several multicast groups and does not show I/O data addressed to a single consumer, I think this was taken from a nonmirrored, unused port, which means that IGMP Snooping and Querying is not set up properly on this network.

In addition, it shows the List Identity requests from RSLinx Classic being repeated extremely fast; 12 times in about 9 milliseconds.

In my experience, RSLinx only sends out a browse packet once every second.

Either RSLinx is behaving in a way I've never seen it, or something in the switch configuration is causing it to echo or repeat specific subnet broadcast packets.

This might explain why the drives fault when RSLinx browses; the large amount of broadcast traffic that appears on the network may confuse their Ethernet cards.

I have never configured these specific switches; you're going to have to bring in some IT-types or give it a shot yourself.

Before you do anything, connect Wireshark to an unused port and perform a capture. If unconstrained multicast data is present on the port, you'll see many hundreds of UDP frames per second.

What you're looking to do with IGMP is to set up IGMP Snooping, with one of the switches also set up to be an IGMP Querier.

Good luck !
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