Ethernet ring topology - redundant

Hi everyone! It´s just a begginer question, isn´t a real case:

In a ethernet ring topology, I read that especific protocols take care about the redundancy (RSTP, STP, etc).

Question: If I have 4 swtches in this ring, all of then need to be managed? It´s possible to use just 1 managed and 3 unmanaged? All elements need to be RSTP able?

Thanks in advance!

I do not know of any unmanaged switch that supports any kind of ring protocol so, yes, you need all the switches IN THE RING to be managed.

Also, it worth to note that very RSTP and STP isn't fast enough for industrial application, therefore, each vendor comes up with their own version of ring protocol so you also need to match the exact brand and product-line.

I would not bother with a ring within a plant, they are not worth the trouble. Use star or redundant star.

Only between buildings, plants, cities etc would I consider a ring topology

harryting said:

I do not know of any unmanaged switch that supports any kind of ring protocol so, yes, you need all the switches IN THE RING to be managed.

Also, it worth to note that very RSTP and STP isn't fast enough for industrial application, therefore, each vendor comes up with their own version of ring protocol so you also need to match the exact brand and product-line.

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Agree that STP/RSTP aren't typically fast enough for industrial applications, and that managed switches are definitely required. However, there are some protocols I've seen that are at least somewhat multivendor.

MRP is built into a lot of Profinet devices, and is supported by switches from at least Cisco and Hirschmann, in addition to Siemens. Claims to have a max 200ms failover for 50 devices in the ring (note that's a max, many other protocols advertise a minimum)

HSR is a bumpless ring architecture, where the packets are sent both directions. Again, I've seen support from Cisco, Hirschmann, and Siemens. Downside here is that few devices will support this, probably only switches.

DLR is tied to EIP, and I've seen support from Cisco, Hirschmann, and Rockwell.

V0N_hydro said:

I would not bother with a ring within a plant, they are not worth the trouble. Use star or redundant star.

Only between buildings, plants, cities etc would I consider a ring topology

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Actually, I routinely use rings inside plants. Lots of benefits, particularly with on-machine devices. Or maybe I should just say star is fine, but NEVER use linear in a production facility.

Also, you might look into REP. I typically use this along with DLR.