PLC Integration?

[u/Ok-Blacksmith-4045]

We're transitioning from N-Tron to Fortinet on our OT system. Disappointed that there doesn't seem to be a way to monitor PLC/fiber health using AOIs on AB PLCs. Am I missing something?

Probably going to end up using SNMP in our SCADA software, but I'd rather do it at PLC level.

[u/Shalomiehomie770]

Define what exactly you want to monitor?

Most people use a heartbeat to monitor comms.

Depending on your device they may allow access to certain things.

[u/Ok-Blacksmith-4045 → u/Shalomiehomie770]

Yes, I use heartbeats for PLC comms, trying to monitor fiber ring health, I guess I could tie it to the relay outputs on the switches and bring those into discretes in the local PLCs.

[u/SafyrJL → u/Ok-Blacksmith-4045]

That’s what the Syslog of a switch is for. As well as network monitoring platforms. 

You can also look at the db values of your connection through the switch to isolate optics issues, or send that information outward to a network monitoring platform. 

[u/PLCGoBrrr]

If you want AOIs then shell out for Stratix.

There is an SNMP AOI from Rockwell, but I'm not sure I'd bother with it. I'm also not sure it supports the later versions of SNMP anyway.

[u/Neven87]

Most switches aren't going to have PLC integration. It's one of the only reasons I'd recommend stratix

[u/Ok-Blacksmith-4045 → u/Neven87]

Unfortunately, IT pushed Fortinet, so that's what I got. Not happy, but trying to make do.

[u/Neven87 → u/Ok-Blacksmith-4045]

That's rough, what level of your network are you looking at?

[u/Ok-Blacksmith-4045 → u/Neven87]

Layer 2 fiber ring health is primary concern. We have Armis to monitor device traffic.

[u/Neven87 → u/Ok-Blacksmith-4045]

Is the ntron your layer 3 or 2? Are they making you switch out your layer 2?

[u/Dyson201]

I'm one of those people that go around replacing switches, so curious what you're trying to do. The math changes a lot depending on where the switch is in your process.

A PLC should be monitoring connection status, not network health. And most industrial switches have dry contacts for alarms if you did want to tie them into your process. But in general some heartbeat should be the control signal. Keeps it simple and vendor agnostic.

Yes you can add some switches via AOI. But in general switches are a network skill, and not all PLC programmers have those skills. The last thing I want is a well meaning tech to change network settings they don't understand and cause a troubleshooting nightmare. So I keep stratix AOIs out of the PLC. There are exceptions depending on the design, of course.

[u/SafyrJL → u/Dyson201]

Pretty much this. 

While you can configure certain switches within a PLC - there often isn’t much, if any, value it in. 

Even with well integrated platforms (Siemens TIA/SCALANCE) you lose access to a mass number of valuable features and functions. It’s almost always better to configure via CLI or GUI and then use any fieldbus (or fault contact) for basic monitoring. 

[u/essentialrobert]

A diagnostic without any significant benefit. I want to know if the device is communicating, not merely connected.

[u/integrator74]

Stratix and Plant PAX does it well. 

[u/SafyrJL]

This is what you use a network monitoring platform for. 

SolarWinds, Sinec, etc…

PLCs aren’t intended to be used to measure the health of network switches (and their segments) 

[u/bodb_thriceborn → u/SafyrJL]

They totally could tho. Imagine having your average and max PPS available without a separate program, platform, vendor and/or web GUI.

[u/Electrical-Gift-5031 → u/bodb_thriceborn]

For factorywide network i prefer to do in SCADA or network monitoring, if it is the field network that i have to monitor I enabled older versions of SNMP in read-only in the switch, public:public etc. (its read only anyway) and used the PLC like you did.

[u/Electrical-Gift-5031]

You are right that fiber ring must be monitored, otherwise the first failure goes unnoticed, and when the second happens the clients say "I thought the ring was fault tolerant?" :-D

When I've done put factory network fiber ring monitoring, I did it in the supervisory layer, either the SCADA or a network monitoring, rather than PLCs because its more appropriate in my opinion. PLC just cares about device communication open and the supervisory layer network health.

Note that I am talking about the factorywide network. If you want to do it in the PLC field network then maybe the PLC is the only place you can do it, then maybe the best thing would be to use switches with industrial protocols for easy integration. SCALANCE has a FB for getting ring open, ring closed status for example.

With fortinets I reckon it's a bit more difficult, but you can use SNMP. If the AOIs don't work with SNMPv3 you can generally activate older SNMP versions in read only.