Network Question

[CENTER]

I was wondering if someone could explain how the Ethernet connection works on this machine and at the same time help me solve this problem. I have a system that is using a 1756-L81ES Safety Controller running Logix Designer 32.03.00 with an IP address of 192.168.20.101 a 1756-EN2TR with an IP Address of 192.168.1.101. 1 MGuard switch and 1 Moxa switch.
The problem I am having is one of my laser gauges died and needed to be replaced, Set the IP address 192.168.1.201 and plugged it in and shows faulted on the control organizer. I can ping it from the Moxa switch so I know the connection is good. I have a second guage .200 that works fine. Now as a side note I thought I should be able to connect to the L81 using Moxa switch by going through the EN2TR. I can open it in RSLinx Classic but not under Who Active in Logix. Any suggestions would be appreciated.

 

[Ken Roach]

The 1756-L81ES controller has a built-in Ethernet port, so that's why it has a different IP address than the 1756-EN2TR module in the same chassis.

Usually that would be done so that the control system can run physically and logically separate networks. Maybe your onboard L81ES Ethernet is connected to an enterprise network and the 1756-EN2TR is connected to the machine devices and I/O network.

In general, a private subnet like you describe has the first three octets set the same, so that 192.168.20.0-254 is one network, and 192.168.1.0-254 is a different network. That is done by settings the subnet mask to 24 bits, i.e. 255.255.255.0.

If your laser gauges are on the 192.168.1.x network, then they need to be configured in the I/O tree under the 1756-EN2TR, and physically connected to that network.

How are the MGuard switch and the Moxa switch interconnected, if at all ?

You should be able to connect to the PLC either through its onboard port or through the 1756-EN2TR. It makes sense to me to set up your laptop with a 192.168.1.x address and connect to the same physical network as the laser gauges so you can configure them and connect to the ControlLogix.

 

[Ken Roach]

Aside: Even in the simplest automation networks, always make a document with a cheat sheet of IP addresses and subnet masks and default gateways and which switches are being used.

Even network experts can get confused and make mistakes and leave things halfway or temporarily configured. Making sure your successors understand the basics when they start connecting can save so many future problems.

I had to phone-support a system a few days ago that used ten machines with Stratix switches. Every machine was identical, with 192.168.1.y addressing, and then the Stratix have been set up with 1:1 NAT so every address on each machine has a 10.1.x.y address on a system network, where .x is the Machine Number, and .y is the same as on the sub-networks.

But none of the cables were labeled. And there was a dual-link architecture that was tried then abandoned, so there were unplugged-on-purpose cables in the cabinets.

So when RSLinx Enterprise suffered from a schema corruption after an unscheduled power dump of the server, nobody knew where to start and just began frantically PINGing and plugging in cables to adjacent ports.

If they had left the cables alone, it would have saved a lot of troubleshooting, but instead two of the machine networks were connected both to their internal switch and the enterprise network, so there were dozens of IP conflicts. Whichever device got power cycled next was able to show up, but because they were the same kind of device, using RSLinx always looked the same.

And of course nobody would admit to having plugged anything into a different port.

When it was all finished, one of our very bright junior engineers asked "Ken, how do you know so much about network troubleshooting ?"

"I've been making mistakes a lot longer than you have."

 

[CENTER]

That maybe what is going on here. The cables are routed as follows, from the L81 to the MGuard Switch, MGuard to the EN2TR, EN2TR to the Moxa switch.

 

[BachPhi]

Nice pic , but clear as mud.

Try unplug the cable from Mguard to EN2TR.

Have you setup the new replacement laser gage, beside setting up its IP address?

 

[BachPhi]

The site is deplorable SLOW.

 

[CENTER]

Yes its setup. What I don't understand is when I connect to Moax switch I can ping the guage and the EN2TR. But still the prossesser doesn't see it.

 

[BachPhi]

• Did you try unplug the cable from Mguard to EN2TR?

Your safety system did not have a safety partner which makes it SIL2 level only.

Can you get another screen shot with system ONLINE showing EN2TRs & Ethernet Modules?

Have you ensured that the replacement part is exactly the same , that is Ethernet/IP and not Ethernet Modbus TCP?

 

[CENTER]

Taking a long weekend will be back to the site next week will update then. Thanks for the help.

 

[CENTER]

Update

I didn't have a lot of time to spend on this today. Other machines down, but I had time to check out the error code and on the guage the only coms I can change is the IP address. Sending a Email to China hope they can help.

 

[Ken Roach]

From a PC connected and configured on the 192.168.1.x network, check the protocols that the device is configured for, using Windows PowerShell's Test Net Connection command.


tnc 192.168.1.201 -p 502


tnc 192.168.1.201 -p 44818

That will tell you if it's set up to respond to Modbus/TCP (Port 502) or EtherNet/IP (Port 44818). RSLinx ought to also see it in a browse if it's set up for Port 44818, though third-party support for RSLinx browsing might not be dependable.

And of course do the same thing for the one that works correctly.

 

[CENTER]

Thanks I will give it a shot next time I'm out there. Luckily it's not a urgent problem.