I am trying to troubleshoot a Modbus TCP gateway that has been working for years. In the last few months, we have been getting very few readings from any of the clients on this gateway.
I have tried replacing the gateway with an identical device and with a device in the same family, but I still cannot get the data on a reliable basis.
I did find out that our IT Department recently replaced the switch that the Modbus TCP gateway was connected to with a Cisco 3850 switch.
I found two documents on the Cisco site stating that Modbus TCP could cause issues with Cisco Switches.
https://www.cisco.com/c/en/us/td/docs/routers/connectedgrid/switch_module_swcg/cgr-esm-configuration/modbus_tcp.pdf
https://www.cisco.com/c/en/us/td/docs/switches/lan/cisco_ie5000/software/release/15-2_2_eb/configuration/guide/scg-ie5000/swmodbus.pdf
Neither one of these documents or anything else I can find on the internet says anything about the 3850 switch family being affected by the above problem.
Does anyone have any incite on Modbus TCP over a Cisco 3850 switch?
