PROFINET Can (Still) Use a Cheap Switch

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If you want to get someone to remember something you can’t repeat it too many times. Case in point: I saw another new blog post from someone who thinks you cannot use a standard Ethernet switch for PROFINET.    YOU CAN!

Seven years ago, I blogged that PROFINET can use a Best Buy Ethernet Switch, really?

Some things have changed in the intervening years, but the ability to use an inexpensive Ethernet switch for PROFINET is a constant. What has changed? It turns out the best buy is not at Best Buy. For this year’s PROFINET one-day training classes we’ve added an inexpensive Ethernet switch in the PROFINET network. But it’s a Netgear switch from Amazon for 18 bucks. It meets the minimum requirements for PROFINET: 100Mbit/s, full duplex. Yes, those are the only requirements. Now to be fair, this switch is designed for the office although it does have a metal housing. It also runs on 12VDC from a transformer that plugs into a wall socket; not real convenient in our typical 24 VDC cabinets. And, of course, it’s an unmanaged switch. And you know what I say about that: you’ll either use a managed switch or wish you had. I ranted about this topic long ago; revisit Managed or Unmanaged Switch for PROFINET.

 

PROFINET with Cheap Switch (Custom)

So how does PROFINET achieve speed and determinism? It’s not magic. We use a standard IEEE field called EtherType to tell the PROFINET real-time frame to skip directly to the PROFINET application. See how well that works in this blog post: Choose the Network First.

Or attend one of our free PROFINET one-day training classes.

–Carl Henning

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