Industrial Ethernet Design

I'm a network admin in a small manufacturing plant, and as part of my responsibilities, I oversee all the Ethernet in the plant. During a
recent network issue (a loop caused by a maintenance tech plugging both ends of a patch cable into the same switch), it was discovered that our Ethernet-enabled PLCs were connected to the same physical network infrastructure as our IT-Ethernet network and given a separate, non-routeable IP address space.
I don't know when this occurred, but it was done years before I was hired and I suspect that it was done the way it was to keep costs down. However, I do need to clean this up as I clean up the rest of the facility's network.
Do PLCs and any terminals that communicate with them need to be on a separate physical network (not plugged into my switches), and are there any good sources/best practices that I can read up on how to implement an industrial network? Are there any products available that would allow me to restrict access to the network based on their login credentials?
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OOOh, that will be a problem. It is best that you take the attitude that you help whom ever is in charge of the plant floor. If not there will be resentment.

Yes. This has been discussed many times on www.plcs.net.

Yes. I am not sure about login credentials. From the plant floor stand point it means having access to a laptop that has access to wireless network. One must separate the office network from the plant floor network using a router. The PLCs on the plant floor should have an Ethernet address such as 192.168.XXX.YYY where XXX is the machine center and yyy is the controller IP address within the machine center. There should be a router that keeps the traffic from one machine center from interfering with another machine center. In addition the plant floor must be separated from the office by a router. Sometimes managed switches will do but it is imperatives that copying a file in the office does not interfere with the plant floor or traffic on the plant floor traffic does not interfere with the office. However, the office should be able to access a specific machine and the plant floor should have wireless Ethernet so the PLC programmers can program their PLC from anywhere on the plant floor.
If you are using Rockwell Automation PLCs then understanding routers and localizing traffic is very important because Ethernet/IP allows all the slave device to transmit their status a specific intervals. The default is 10 ms. This can swamp a network that doesn't localize traffic.
Cooperate, separate, don't try to dominate you will have much more success.
Peter Nachtwey
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Here is one site that might help
http://ethernet.industrial-networking.com /
Steve MTL www.mtl-inst.com
Sean wrote:

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