Connecting to S7 300 over NAT not possible

[ferdoo]

Describe the bug

I can not connect to IM151-8 PN/DP CPU (6ES7 151-8AB01-0AB0) when is behind NAT. Im connected to this CPU from another CPU using PUT/GET over NAT and this work. Im able to connect to CPU1500 over NAT this olso works.

To Reproduce

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4. See error

Expected behavior

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Flow

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Environment

• Version of this node: [e.g. 2.1.1]
• Node-RED version: [e.g. 1.0.3]
• PLC Part Number: [e.g. 6E57-... ]
• OS: [e.g. Windows 10, Ubuntu]
• Browser: [e.g. chrome, safari]

Additional context

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