# Troubleshooting Ignition to M340 PLC over Modbus TCP **URL:** \ **Category:** Ignition\ **Tags:** modbus, ignition81, perspective\ **Created:** [December 3, 2025, 12:40am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578 "2025-12-03T00:40:08Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ericksone](https://avatars.discourse-cdn.com/v4/letter/e/43a26b/32.png) [@ericksone](https://forum.inductiveautomation.com/u/ericksone)\ **Post date:** [December 3, 2025, 12:40am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/1 "2025-12-03T00:40:08Z")
I have an m340 PLC using a P34-1000 card (ver 3.5) and a NOE 0100.2 (ver 3.5), ignition modbus driver is 7.1.35. This is behind a tailscale router with the ignition server on the tailscale network as well. I am able to ping the PLC and modscan it with the correct addresses from a computer remotely through the tailscale network but ignition will not create a connection to the device in OPC devices. logs are not giving me much information to troubleshoot why it is not connecting. opcpath: ns=1;s=[{OPC\_Device}]1.HR261.0. ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/7/d/7db0b3367e9dd92054ce88ac4f7978996fdc549d.png) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/d/b/db8c69002d92150b7680a952a85bce77958933db.png) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/0/f06223c4c43d8e24bf50bf7f0455dbdea63afbb2.png) ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 3, 2025, 12:53am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/2 "2025-12-03T00:53:39Z")
If the connection does not show "Connected" in the devices section, you have likely a config issue or a network issue. Can you ping the PLC from the ignition gateway itself? ---
**Author:** ![ericksone](https://avatars.discourse-cdn.com/v4/letter/e/43a26b/32.png) [@ericksone](https://forum.inductiveautomation.com/u/ericksone)\ **Post date:** [December 3, 2025, 1:05am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/3 "2025-12-03T01:05:55Z")
yes i can ping it from gateway ---
**Author:** ![ericksone](https://avatars.discourse-cdn.com/v4/letter/e/43a26b/32.png) [@ericksone](https://forum.inductiveautomation.com/u/ericksone)\ **Post date:** [December 3, 2025, 1:11am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/4 "2025-12-03T01:11:00Z")
nevermind, i thought it could but just tried to ping it again and it will not work. ill go down that route ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 3, 2025, 1:24am UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/5 "2025-12-03T01:24:48Z")
If you can modscan it from the gateway, the ignition side will be pretty straightforward to set up. ---
**Author:** ![ericksone](https://avatars.discourse-cdn.com/v4/letter/e/43a26b/32.png) [@ericksone](https://forum.inductiveautomation.com/u/ericksone)\ **Post date:** [December 3, 2025, 3:02pm UTC](https://forum.inductiveautomation.com/t/troubleshooting-ignition-to-m340-plc-over-modbus-tcp/112578/6 "2025-12-03T15:02:21Z")
it was a tailscale routing issue, got that fixed and now ignition can talk. Thank you.