# Modbus TCP configuration error

**URL:** <https://forum.inductiveautomation.com/t/modbus-tcp-configuration-error/113484>\
**Category:** Ignition\
**Tags:** ignition81\
**Created:** [January 22, 2026, 3:55pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-configuration-error/113484 "2026-01-22T15:55:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Henk](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@Henk](https://forum.inductiveautomation.com/u/Henk)\
**Post date:** [January 22, 2026, 3:55pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-configuration-error/113484/1 "2026-01-22T15:55:39Z")

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We are getting an error message on a tag after adding a this tag in a new project:  
Error\_Configuration(“Bad\_NodeIdUnknown. The node Id refers to a node that does not exists in the server address space“)

Were can I find this Node Id?

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [January 22, 2026, 4:07pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-configuration-error/113484/2 "2026-01-22T16:07:41Z")

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That error is presumably on an Ignition Tag where you’ve specified an OPC Item Path that is not valid Modbus address syntax. The user manual describes the syntax in detail.

What’s the current OPC Item Path?