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GX WORKS3 • FX5U / GX WORKS3

Why did my FX5U Ethernet parameter change not take effect?

After writing applicable Ethernet parameters, the CPU may need a reset or power cycle before the new settings become active.

Practical explanation

The hardware manual explicitly describes writing the parameters and then resetting or cycling power for the settings covered by that procedure.

Plan the interruption because communication can be lost when the IP address changes.

Check in this order

  1. 1Save a backup first.
  2. 2Write the correct parameter set.
  3. 3Record the new IP settings.
  4. 4Reset or cycle power only when the machine is safe.

Safety: Never reset a running production controller without approved downtime and a safe machine condition.

Last reviewed: 2 October 2026

Official source: FX5S/FX5UJ/FX5U/FX5UC User's Manual (Hardware)

Related verified answers

How do I connect GX Works3 directly to an FX5U by Ethernet?How do I connect GX Works3 to an FX5U through a network switch?Should I read the PLC program before making an FX5U change?

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