I am trying to support two network Logo controllers that were installed by an electrician who is no longer available to support the install.

The two logo's seem to be operating properly.  They both have a proper IP/subnet mask/gateway.  I can ping both devices, and connect to both via the programming software.

The master cannot control the slave, however.  The screen on both end periodically shows Errors Occurred.  The log shows "ID 6: Network Access Error".

I am a network admin by trade, not a PLC programmer.  I have confirmed that layer three connectivity is good.  However, I cannot get the 2 to communicate.

How can I further troubleshoot this short of just buying another to replace it?  I don't have immediate access toone.

I don't know the model numbers, but I could drive out and look.

The Master PLC firmware says: 0BA7.Standard V1.03.32

The Remote PLC firmware says: 0BA7.Standard V1.03.32

Thank you.

The master connects via Ethernet to a Cisco 3850 switch.  That switch is connected via Ethernet to Netgear switch.  That switch is connected via Fiber (and ethernet to fiber transceiver) over to the liquid tank where the remote unit is.  The fiber connects to a small netgear switch at the tank (via another ethernet to fiber transceiver).  And the remote unit connects to that same netgear switch.

When I did my network testing, I had my laptop plugged into the Cisco on the master side, and the netgear on the slave side. 

So, found a solution.  but I think the "network access error" was a red herring.  It seems that every time I rebooted one of the 2 PLC's, it would log that error, and just keep flashing it.  So maybe it was all a misunderstanding on my part.

Regardless, I did get the code working.  I was able to find a not statement that was missing. (Can the code get corrupted and change itself?)