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FCS/Dup Ack/Retransmit

Hi all,

My first post here and hope I can get some insight to an issue we are having at one of our facilities.

We recently upgraded all of our un-managed 10M/HD switches to 10/100M/FD managed switches and encountered an issue that has stumped others and an integrator we had on site.

The communicating equipment is a Modicon M340 and an Eaton VFD drive with a Modbus TCP adapter (OPTCI card).

There are 12 devices in this comm path and 6 are having issues talking back to our PLC (all on the same switch, the local switch is a N-TRON 7900 series managed switch 10/100 / non Gb)

Previously, all 12 Eaton drives had a similar issue, although we were able to force a duplex mode on 6 of the Eaton drives (Using a different model Modbus TCP card) and the issue stopped (we forced a 10M/FD mode).

With the other 6 drives, we are unable to force the duplex modes (appears to be an issue with a software revision or firmware) and those 6 are the ones giving us trouble.

Eaton claims the auto-negotiation should work fine, although I have read that there is a possibility some manufacturers have different implementations of "auto-negotiation".

It appears the 6 drives are in "auto negotiate mode", but when we set both sides to auto-negotiate (we can set this in the switch and we assume the drive is auto-negotiate/we can not see or change this setting) the drive fails to communicate and the switch claims a 100M/FD mode.

I am assuming I am seeing a Duplex Mismatch (in my wireshark capture), although I can not confirm this.

Is there any chance someone can take a look at my capture and provide some feedback?

Thanks all and if more info is needed I can provide it asap.


*It appears I can not attach a file -- here is a link to my capture --