“I work in Siemens-based environments where S7‑300 and S7‑400 PLCs are still critical for production. We already use PRTG successfully for IT and network monitoring, but for these legacy Siemens PLCs we can currently only monitor basic things like ping or generic SNMP.

That means:

We see that a PLC is reachable or not, but
We don’t see WHY it went into trouble (STOP, restarts, cycle time issues, hardware faults, battery, etc.)
In real incidents, we still have to open STEP 7 / TIA Portal or go on site to look at the diagnostic buffer and CPU status. This is slow and painful when a line is down.

What I would really like PRTG to do for Siemens S7‑300/400 (via the S7 protocol) is
1. CPU / PLC status which have the details like:
RUN / STOP state
Fault / error status
Warm vs. cold restart count
Timestamp of last restart
2. Performance and stability:
Cycle time (scan time): current, min, max, average
Ability to trend cycle time over time
Thresholds/alerts if cycle time suddenly jumps or jitters
3. Hardware / diagnostics:
Battery status
Diagnostic buffer / last X fault entries
Rack/module diagnostics (missing module, hardware failures)
Map important ‘LED-like’ states into clear channels (e.g. OK / warning / error)
4. Alerting and reporting:
Alerts if PLC goes to STOP, restarts too often, or cycle time exceeds limits
Historical graphs for cycle time, restarts, and faults
Simple reports for audits and maintenance reviews.

Our IT already trusts PRTG; we would like to use it as a real IT/OT monitoring cockpit, not just for network and servers