Ring network issue with Modicon M580

[doomsword]

So, I have either interesting or stupid problem.

We have ERIO network which we would like to be in a ring topology. Our ring master would be M580 eH58 4040 (hot standby) PLC, which is actually two PLCs (A and B), where one is a STAND-BY PLC while other is in RUN.
ERIOs are now powered and everything is visible on a network. When we close the ring interesting thing happens - our network starts to flicker. What I mean is that every 10 to 20 seconds network goes down for a 1-2 seconds approximately, visible online with PLC and red lights also appears on PLC and Ethernet RIO heads.
When we make a break and make a network linear we have no issues, everything runs smoothly.


I'm sure hardware is properly configured, CPU is a root on RSTP while CRA 312 00 are defined as participants.
We have NRP 312 00 fiber optics converters which we use to to enable fiber optics ring configuration.
I'm curious about what do you think could be a reason that fiber optical ring network doesn't work? If RSTP is configured properly then there should be no problems. NRP cards all have correct light indications showing communication exists (R and T ports seem to be matched correctly). I've noticed that FX light goes continuously green when this problem happens, usually it flickers, don't know if it indicates something.


Any idea where to look for a problem is appreciated, especially that nobody here has much experience with Modicon PLCs.

 

[V0N_hydro]

what if you close the ring so that it starts to flicker, but then open the ring somewhere else? Does the last connection that has been flickering continue to flicker?



Maybe it is bad luck that the last connection in the ring that you have been closing has some issue, as opposed to a larger problem with the ring configuration.

 

[doomsword]

We tried disconnecting and connecting ring in various places and every time it seems that closing the ring is the problem. Entire ERIO network goes down.


Also another suspicious thing I noticed happening (at least once) is that according to converter card optical ring died when we powered off and powered on remote rack where we first noticed this problem so we thought it was that rack problem, while we didn't change anything regarding T and R port connections (all was good). When I cycled power in a remote rack to which suspicious one was connected link was reestablished but of course, flickering continued after a while.

Tomorrow we plan to check in details all remotes to see if we can find anything suspicious.
For me seems more like some ring management issues, rather than wrong wiring. We don't have any switch inside ERIO, just a ring connection of all remote heads with copper or through optical converters.

 

[Lare]

M580 have three eth ports. Are they connected and configured right. (Service port should not be connected now I think)

Also is this new setup or is problem only started now and worked before

 

[doomsword]

M580 have three eth ports. Are they connected and configured right. (Service port should not be connected now I think)

Also is this new setup or is problem only started now and worked before

This is new PLC in old plant, first time we try it. Pretty much exactly same project was done last year, and comparing it all regarding RSTP configuration is the same and network structure is the same, except one more remote exists in this project, which means just additional two optical links.


I just don't know where I could look in Unity Pro to see if I made something wrong or I need to check remote racks thoroughly tomorrow.

 

[Lare]

Are all optical links Schneider's?

 

[doomsword]

Are all optical links Schneider's?

Yes, everything in ERIO is Schneider produced, no any 3rd party switches or anything like that.

 

[Lare]

CRA and NRP should connect this way
https://www.schneider-electric.com/en/download/document/EAV19662/

 

[doomsword]

In the end it was a stupid problem.


Yesterday I found one Ethernet cable had a bad connector, I presumed this since both sides were powered on and no communication was going no matter how much I tugged connectors on both sides to achieve connection, so I told one electrician to check it.
One hour later it was confirmed it was connector problem and it was fixed and I could see the RIO online so I thought connector issue was fixed. By the end of the day entire network was established and then this problem with ring started happening.
So we started checking RIOs this morning one by one and when we came to this particular cabinet and cable we saw the electrician or some other guy put it in service port of Ethernet head. Putting it back to correct port resolved the issue with the ring network.