# Problem with s7-1500 and NAT

**URL:** <https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929>\
**Category:** Industrial\
**Created:** [3 September 2025 15:15 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929 "2025-09-03T15:15:58Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![DWoodlock](https://avatars.discourse-cdn.com/v4/letter/d/49beb7/32.png) [@DWoodlock](https://discourse.nodered.org/u/DWoodlock)\
**Post date:** [3 September 2025 15:15 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929/1 "2025-09-03T15:15:58Z")

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Hello all,

Been working on setting up a large network of s7 machines, and then using NR to retrieve some signals, turn those signals into count and then sending periodically to maintain x.

Most of my stufff is working as intended, but I have run into a problem while using a NAT device on one of our machines.

It is a s7-1500, and I’ve used the NAT to translate from 192.168.1.10 on the lan to 192.168.11.10 on the wan port.

I am using node-red-contrib-s7 and I’ve basically opened all the ports in the nat, and tried multiple devices and yet to achieve sustainable functionality. There’s been a few instances where I’ve gotten it to work for a period of time, but if I restart either NR or the machine it won’t reconnect without physically disconnecting adapters and reconnecting.

Just wondering if anyone else has run into issues with this or can propose a solution.

Have a handful of machines which will require a NAT device, I purchased this one Wall IE by system Helmholz because in years past we had good luck with their devices but at the moment struggling.

I am able to connect to the PLC through the NAT device using my programming software, so not sure what the obstacle is for NR

Thanks in advance

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**Author:** ![DWoodlock](https://avatars.discourse-cdn.com/v4/letter/d/49beb7/32.png) [@DWoodlock](https://discourse.nodered.org/u/DWoodlock)\
**Post date:** [3 September 2025 18:31 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929/2 "2025-09-03T18:31:33Z")

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Think I got it sorted now. Networking noob challenges I think. See how it does after a few days and report back.

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**Author:** ![DWoodlock](https://avatars.discourse-cdn.com/v4/letter/d/49beb7/32.png) [@DWoodlock](https://discourse.nodered.org/u/DWoodlock)\
**Post date:** [5 September 2025 22:13 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929/3 "2025-09-05T22:13:13Z")

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System has been working fine since last report.

I think the root of my problem was not understanding subnet masks. I altered my approach and everything all of a sudden worked.

I thought if I changed my subnet mask to 16 from 24 it would allow me to reach all devices in the 192.168.###.### range, and although it worked a handful of times. If I broke the link say by restarting the rpi that was running NR it would not establish without doing a bunch of physical disconnecting of devices.

solution was to assign multiple static IP addresses each with a 24 mask from my NR device.

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**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [6 September 2025 05:47 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929/4 "2025-09-06T05:47:13Z")

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192.168 addresses are in the class C range so are expected to only have a 24 size subnet. So devices would default to that and not route beyond it by default. Eg see [IPv4 Addresses Classes Explained: A Comprehensive Guide to Class A, B, C, D and E](https://www.meridianoutpost.com/resources/articles/IP-classes.php)

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [5 November 2025 05:47 UTC](https://discourse.nodered.org/t/problem-with-s7-1500-and-nat/98929/5 "2025-11-05T05:47:34Z")

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Closed on 5 November 2025 05:47 UTC

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