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Old October 23rd, 2011, 08:33 PM   #1
daba
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Logix5000 Produce/Consume Tag Errors...

A puzzler...

Scenario -
1 "Master" ControlLogix L73, and 7 "Slave" ControlLogix L61 - all Version 19.
All chassis interconnected via a "Ring" network using 1756-EN2TR modules, rev. 4
Also there is an "IP" network to all chassis, using 1756-EN2T modules, rev. 4, connected via SixNet managed switches - "out-of-the-box" configuration.

Produced/Consumed tags, going both directions, (i.e. master to slave, and slave to master), have been configured.

The producer tags are configured each for 2 consumers, and these are consumed into separate tags in the consuming PLC via the "Ring" network, and the IP network.

The idea is that the IP tags are a redundant backup for the Ring network tags, the Ring only having single point failure protection.

We cannot get the IP tags to work, even though the setup has been checked, double-checked, and checked again. The "Ring" connected tags work correctly.

Specifically we get error 16#0203 "Connection Timed Out" on the processors in the IP branches of the I/O configurations in all projects.

This error indicates the connection is established, but the data transfer did not complete (it depends where you read about the error code).

However, I have added the member "Connection_Status" to the tag UDTs, and we are seeing that the connection is not established.

We do not have a problem with the number of connections, well within capabilities.

All tags are set to "Multicast", since this is a redundancy system, with 2 "Master" PLCs, Unicast is not allowed in redundancy systems, as it disqualifies the redundant chassis.

The Sixnet switches all have IGMP enabled (default).

This must be a simple thing to fix, but we have not got anywhere.

Can anyone shed any light on where the problem might be, as RA tell me this configuration should work.
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Old October 23rd, 2011, 08:56 PM   #2
Ken Roach
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Is the "Master" PLC, the 1756-L73, the Redundant Pair ? Or are all of the controllers Redundant Pairs ?

Have you tested an alternate tag on the "IP" network that isn't also being Produced on the Ring network ?

I would put Wireshark on one of the Producing 1756-EN2T's on the Ring network and see if it's even attempting to make the connection. I think you can see the Consumer request the Producing tag by name in the Wireshark trace, which helps narrow down the traffic fast.

Remember that if you use Connection_Status, you need to use it everywhere; it actually modifies the Produced datatype so you can't consume a tag with Connection_Status on one network and consume the same named tag without Connection_Status on another network.
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Old October 23rd, 2011, 09:28 PM   #3
daba
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Understood Ken...

"Master" PLc has a redundant pair only, the other 7 PLCs I called the "Slaves" are standalone.

Good idea to add another tag that isn't also consumed via the Ring network - i'll try that.

I can see the connection being attempted in the controller properties connection tab - it cycles "connecting - faulted" etc.

Connection_Status has been added to all of the tags.

Don't forget each tag is produced for 2 consumers. Its the consumers that have the 2 entries in the I/O configuration, one on the ring, and one on the IP network. The Ring P/C tags work fine, just the IP ones don't. I'm beginning to think it's a switch issue, although I've been told the out-of-box configuration should allow this.

I can post cut-down projects later today for you to look at if you like.
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Old October 23rd, 2011, 11:29 PM   #4
Ken Roach
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The cycling of the connection status between "Connecting... Faulted... Shutting Down..." points to a multicast routing issue.

The establishment of a Produced tag cyclic connection runs over ordinary TCP connections, so it succeeds. The Produced Tags go over UDP with a multicast destination address, and they're getting mis-routed or blocked or filtered out, so the I/O connection fails after 4xRPI. The connection gets canceled, then re-started, and the whole thing happens again.

I'll bet if you put Wireshark onto a tap or a mirrored port connected to the Primary 1756-EN2T that you'll see the connection establishment, then four UDP packets (they show up in bright cyan in default Wireshark color coding) then the connection canceling.

Which model of Sixnet managed switches are you using ?

It's also possible that the Producer is being confused by having two Consumer requests come from the same originating serial number, but the switches are still my prime suspects.

Can you connect just one of the "IP" systems directly to the Primary system, to rule out the switch ?
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Old October 24th, 2011, 08:00 AM   #5
daba
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Quote:
Originally Posted by Ken Roach View Post
Can you connect just one of the "IP" systems directly to the Primary system, to rule out the switch ?
Good idea - Am I right in thinking I will need a crossover cable ?

Or, I have a standard un-managed 8-port NetGear switch I could use....

The IP Network is Fibre, if that makes any difference.
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Last edited by daba; October 24th, 2011 at 08:10 AM.
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Old November 8th, 2011, 06:44 PM   #6
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Just to close this one gracefully....

Everything finally got working, but it required turning OFF IGMP Snooping in all of the SixNet switches.

Now that goes against all the advice I received from various sources, including RA.

I'm not concerned about not having IGMP enabled - this is a private/isolated network and the Produce/Consume tag usage is minimal - 2 tags each way every 50 mS. I don't think bandwidth will be an issue at all.

And just to complete the picture, the IP network around the PLCs is actually a fibre "ring" - courtesy of the SixNet plug-in fibre transceivers (nice kit - only just been introduced to them)
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Old November 8th, 2011, 07:44 PM   #7
The Plc Kid
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Daba

You said all switches were set OOTB to be snoopers but what about queriers?

Most switches OOTB are set for both that I have seen but having multiple queriers in a star or ring system can cause issues.

Just a thought.
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Old November 9th, 2011, 01:40 AM   #8
daba
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I don't remember seeing options to divide IGMP into snoopers and/or queriers when I looked at the system, and looking at the manual again, I believe the "Querier" on the network is automatically assigned to the lowest IP Address.

Also this from the manual...

"Without IGMP, all multicast packets must be forwarded to
all network segments. With IGMP, multicast traffic is only forwarded to network segments, which connect
interested hosts."

Since we have a fibre ring configuration, i.e. only one network segment, does it not follow that to make use of the path redundancy provided by the ring, we should not use IGMP ??



Anyway, IGMP is completely disabled in all switches, and it all works fine.

I won't get a chance to have another go at this, have finished my involvement with the project, but wanted to tidy up loose ends on this thread.
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Old November 9th, 2011, 03:12 AM   #9
Chris Taylor
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DABA

"I won't get a chance to have another go at this, have finished my involvement with the project" you wish!

Only joking, Thanks for your assistance on this one. Full IST went very well for us, no upsets at all even when they tried to load the entire building on one generator, everything loadshed splendidly.

Did I tell you the redundancy issue was to do with Master clock being selected in the processor. Synching in less than 3 mins from a cold start. better the nthe 20 mins it took on the old system

I'll call you after Christmas as it looks like I have another building to do, a bit smaller in I/O but more PLCs

Chris

Last edited by Chris Taylor; November 9th, 2011 at 03:13 AM. Reason: bad spelling
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