TIA V17, CPU 1515F-2 PN, six ET 200SP stations with F-DI and F-DQ modules, all PROFIsafe. We shipped the machine last year on a line topology.
The customer had their switches changed to Scalance XC208 and asked me to configure MRP, which I did on a site visit. Since then the far station on the ring passivates two or three times a day. Their buffer says "F-monitoring time exceeded" on the F-DI, then it reintegrates after an acknowledge.
I tried swapping the IM 155-6 PN HF on that station with a spare, same thing. The customer wants MRP taken out again, "it worked before".
The F-monitoring time is whatever TIA proposed, 100 ms I think, and I never changed it. I'll own that. Fourteen devices in the ring.
Is it the ring, or the monitoring time itself, any thoughts?
Ring reconfiguration time. Standard MRP is the 200 ms class for up to 50 devices, fewer devices is faster in practice but 200 is the figure you design to. A 100 ms F-monitoring time is under that. Is a link in the ring actually going down, though? MRP only reconfigures when something breaks.
Separate the layers before touching the F-parameters. Switch logs first: is a port flapping? Then the ring: does the manager report reconfigurations at the times in the buffer? Then the safety side. If nothing on the ring changes state, the monitoring time is not your problem, the cable is.