Message setup to another network

Ok I'm racking my brain on this. Maybe I'm missing something but I could really use to help. Google gave me many links to here but none of them exactly answered my question. Here's what I have. I have two PLCs on two separate networks that I want to send messages back and forth on. For right now we'll call them 192.168.1.x and 10.10.10.x. This is in a plant so there is networking done behind the scenes that I can't see but those two networks can talk to each other. Right now from my laptop I can ping both networks. So PLC A is on the 192 network and PLC B is on the 10 network. I can see both of them through RSLinx. Is it possible to message between them and if so how is it done? For my current test I have an L72 that is doing a PLC5 read. I have a PLC5 on the same network and the PLC5 read works just fine. My ENBT is called ENBT so my path is ENBT, 2, 192.168.1.5. Now my second PLC5 is on 10.10.10.5. Would be path be ENBT, 2, 10.10.10.5 (which isn't working) or would it be something else? I also noticed that the browse button doesn't do much. Is there a setting to get that to actually browse the network? Over the past 24 hours I've read up on networking, watched videos, and as long as the default gateways are setup properly (which I believe they are) this should work.

So for an answer I'm either looking for the proper way to do it, or to be told nope it just doesn't work that way. In which case I'll just have to buy a second ENBT and put it on the 10.10.10.x network. I've seen that done before. But my IT guy says that since you can ping 10.10.10.x from 192.168.1.x you should be able to message between the two. Any info would be great. Any tech notes on why or why it isn't possible would also be great to read and learn from. Thanks.

You will need the second bridge addressed and networked for/into the 10.10.10.x subnet.

IT lives in their own little world......Automation controllers data exchange is not TCP Ping...

dmargineau said:

You will need the second bridge addressed and networked for/into the 10.10.10.x subnet.

IT lives in their own little world......Automation controllers data exchange is not TCP Ping...

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Does that just mean a second ENBT or are you referring to something else? Thanks.

Your MSG instruction should specify the slot number of the CPU in the remote chassis. Since you can have multiple processors in a single chassis. (For controllogix systems)

EngDave said:

Does that just mean a second ENBT or are you referring to something else? Thanks.

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Yes...The 1756-ENB(2, 3)T modules are EtherNet/IP bridges. They 'bridge' Logix Backplanes to Ethernet subnets.

Because they are two different networks they are more than likely connected to each other via a router. If you want to msg from a PLC on one network to a PLC on the other network, the PLC's need to know to send the data to the router which in turn will forward the data to the appropriate PLC. This is what the "Gateway" address in the network configuration is used for. The router will have at least two IP addresses, the LAN (local area network) address and the WAN (Wide Area Network) or Internet address. The PLC doing the messaging should be connected to the LAN port(s) and that's the address you need in the Gateway setting. This is the same type of setup used to access the internet from your PC. Your PC is connected (or should be connected) to a LAN port on a router that has its WAN port connected to the internet service provider.

Disclaimer, I'm an IT novice at best. I know just enough to be a little bit dangerous. The limitation to recoup any damage received by taking my advice is limited to the price you paid for it (less 10%). However I've recently setup something very similar to what you are trying to do and I was able to make it work. Having said that, I had full access to the router and I disabled the firewalls which may or may not be needed so you're kinda on your own in that regard.

Firejo said:

This is what the "Gateway" address in the network configuration is used for.

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Let me clarify, I'm talking about the network configuration in the PLC. There should be a "Gateway" setting and that needs to have the routers IP address.

EngDave said:

So PLC A is on the 192 network and PLC B is on the 10 network. I can see both of them through RSLinx. Is it possible to message between them and if so how is it done? For my current test I have an L72 that is doing a PLC5 read. I have a PLC5 on the same network and the PLC5 read works just fine. My ENBT is called ENBT so my path is ENBT, 2, 192.168.1.5. Now my second PLC5 is on 10.10.10.5. Would be path be ENBT, 2, 10.10.10.5 (which isn't working)

Click to expand...

Did you get this working? I think Firejo had all of the info that you needed.

I don't have PLC5 hardware to test with.

If you have the message working on a local network ... the method I would use to make the networks 'remote' is to:
- change the PLC5 IP address to 10.10.10.5
- add the gateway address to your L72 ethernet card (we would use 192.168.1.254 on the source L72 in this example)
- add your gateway address to your PLC5 ethernet sidecar (10.10.10.254 would be our convention in this example)
- physically change the IP address of the PLC5 sidecar

then your IT guys would have to route the 2 networks to allow communication between them, using the .254 addresses as the address that triggers each switch that the packets get sent to a different network.

You will have to check with your IT guys to verify the correct gateway addresses to use. And maybe buy them some doughnuts

On your local Class A network where your engineering PC is, run the Windows IPCONFIG /ALL command.

Mine looks (in part) like this:


Because my computer knows that the Gateway for my network is 192.168.100.100, it will accept off-network messages that come from that address.

Your 1756-L72's local Ethernet module (1756-ENBT, 1756-EN2T, etc) needs to have the same Default Gateway as your computer that can correctly connect to the remote PLC-5.

Networking is, obviously a big topic, and I agree that "PING works" is really only the first step.

There's a great tool called "TCPing" that lets you perform a PING-like test to see if a device is accepting TCP connections on a particulary port. You can "TCPING 10.10.10.5 44818" to verify that the remote PLC-5 is running the EtherNet/IP driver in its firmware.

Thank you everyone for helping me out. And thank you Ken for the tool. I will test that out and get back to you.

So a little more to the story. There are actually four networks that are all different but in the firewall / router setup they made rule that basically says all four networks can talk to all four networks. So in trying another network I did get this to work. A bit of a shocker cause I really thought I was going to need a second ENBT or a bridge. But with the tool that Ken mentioned I'll check to see if that port is open on the network in question.

So at the moment the end result is I don't have to reword / re-setup the message block. I thought there might have been something I missed but it doesn't look that way. The issue is probably a rule on the firewall / router side that might be beyond my control. I will give an update on Monday if we have found anything on the router's side. Again thanks for everyone's help.

One more update. Ken I just used the tool you mentioned and the PLC5 on a different network that I was able to message TCPing confirmed that the port is open. The PLC5 I'd like to message to TCPing said no response. So I'll talk with IT and see what we can do. Thanks for the tool!

Another bit of complexity I'll introduce, since you do have TCPING.

The original PLC-5E controllers, 1785 Ethernet sidecars, and SLC-5/05 controllers (circa 1993) had a proprietary A-B Ethernet protocol called Client-Server Protocol. You'll see it called "CSPv4" in A-B documents.

That protocol used TCP Port 2222.

The modern ControlLogix don't support that old protocol at all, and the modern EtherNet/IP (also called CIP) protocol uses TCP Port 44818.

Most PLC-5E and SLC-5/05 controllers built in the last 20 years have firmware that supports both CSPv4 and CIP.

So if you have multiple PLC-5's and TCPING handy, you can probe them by determining if they have TCP Port 2222 and/or TCP Port 44818 open.