This question is an off-chute of my segregated vs v-lan process network thread.

What switches do you prefer to use in your process control ethernet networks? Do you use CISCO or other brand names familiar to the IT world or do you prefer to use hardware that's specifically marketed to the controls world like the ones advertised as Industrial Ethernet switches from Phoenix Contact, Multilin, etc? Also, when selecting a switch, what criteria do you use? Why?

I have never used one...yet. We are looking at putting in an ethernet network for our distributed I/O and data trasnsfer to the office people. I have been looking at N-Tron http://www.n-tron.com for our switches. I have also been told that having a manageable switch is a must. All the industrial switches and ethernet i/p hardware seems to be a bit spendy, but I have been told time and time again that this is not the place to try and pinch pennies, and I think that to be wise advice.

I have had excellent service out of N-Tron switches. I have also heard good things about Hirshmann switches and recently had a look at B&B Electronics which also looked very good

For rockwell Enet select Enet with following Spec

For rockwell Enet select Enet with following Spec

We use Phoenix factory line switches.

Compact and DIN rail mounted.

http://www.phoenixcon.com/ethernet/sf.asp

Excellent Presentation - We are using Cisco Managed Switches for our plant network, but don't have Ethernet I/O in use yet.

You might think about ethernet ring switches. That way you get some fault tolerance.

I use the N-tron switches. The N-tron is a high quality medium priced industrial switch.

I have one managed switch that segregates the controller network from the plant IT network. Then I use smaller N-tron unmanaged switches to segregate the controller network into local PLC/HMI/Programming groups, this way if the managed switch goes out we can still operate disconnected from the IT network, and if any of the smaller switches goes out, we only have downtime in a small workcell while the switch is changed out. To date however, I have never lost an N-tron switch.

I've heard that the Moxa switches (B&B electronics) are a good low cost industrial switches, but I've never personally used one.

Thanks for all the feedback fellas. It's much appreciated.


Can you elborate for an ethernet idiot please? What's an ethernet ring switch.

We use Hirschmann switches, they are excellent and their after sales service has been great. I think Hirschmann is mainly European though as most US networks that I have experienced have Cisco switches but I could be wrong.

Lee

If your plant uses Cisco managed switches everywhere else, then I would suggest Cisco. Cisco switches do alot more than meets the eye......

It's not just a matter of "These switches work good and their cheep". There is alot going on that you don't see. Network devices like switches and hubs don't simply recieve a packet and send a packet. Next, do you want a hub or a switch. A lot of people don't know there is a difference (google it).

There is a protocol called the "spanning tree protocol" and also the newer "rapid spanning tree protocol". These are IEEE standards that some switches have. There are also some proprietary versions of the same thing.

Normally, "loops" in your network are illegal. You have to wire everything as a tree. So this creates a situation where there is always a single point of failure everywhere...if a line goes down anywhere in the network, that portion of the tree is cut off.

A "ring" network eliminates that problem. Everything is in a single loop so if you lose any given link, it turns your ring back into a tree, but you don't have ANY downtime.

The spanning tree protocol effectively constantly maps your network's topology out automatically and allows you to do almost as many "loops" as you want. For instance, you could make a "star" network which allows for maximum bandwidth to and from the hub (preferred for SCADA) but connect the tips of the star together in a separate ring to have 3 alternative paths to and from any given point. A "ring only" protocol would totally freak out at this topology. A spanning tree doesn't care...it just takes the best route every time.

Another advantage of the spanning tree protocol switches is that those extra links can be something much less expensive and slower. For instance, make a star with fiber. Then the extra links could be wireless modems or CAT5E. Then if a fiber link goes down, you're "stuck" with a slow network around one of your switches but only one switch until you make repairs.

It all depends of course on how badly you want/need redundancy and how much you are willing to pay for it.