# Ignition 8.1 Siemens UDT via OPC UA trouble

**URL:** <https://forum.inductiveautomation.com/t/ignition-8-1-siemens-udt-via-opc-ua-trouble/54865>\
**Category:** Ignition\
**Tags:** perspective, ignition81\
**Created:** [January 11, 2022, 9:02am UTC](https://forum.inductiveautomation.com/t/ignition-8-1-siemens-udt-via-opc-ua-trouble/54865 "2022-01-11T09:02:09Z")\
**Posts on this page:** 1\
**Showing post:** 20

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**Author:** ![Matthew\_Hunt](https://avatars.discourse-cdn.com/v4/letter/m/35a633/32.png) [@Matthew\_Hunt](https://forum.inductiveautomation.com/u/Matthew_Hunt)\
**Post date:** [January 12, 2022, 12:57pm UTC](https://forum.inductiveautomation.com/t/ignition-8-1-siemens-udt-via-opc-ua-trouble/54865/20 "2022-01-12T12:57:45Z")

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To make the Solution concrete in case anyone else comes across this issue:

- 1200 PLCs have a different OPC structure from 1500 PLCs due to the setup necessary on the PLC side.

- On the 1500 PLC the checkbox “Standard server interface (SIMATIC namespace)” has to be enabled.

- “Legacy data type definitions” should be enabled on the OPC.

- Do not use the “Server Interface” method when communicating datatypes and structures on 1500 PLCs

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