Linx Ethernet Drivers

[Tim Ganz]

I have several older systems in our plant that use the 1756-ENET card for comms, and we have some with the 1756-ENBT cards as well as one system with a 1756-EN2TR

When I use the RS Linx Ethernet /IP driver I can see all the ENBT cards and the EN2TR card on the network but not any of the ENET cards.

But if I setup an ethernet devices driver and type the IP address in for each system that has the ENET card they show up using that driver and I am trying to understand why this is working this way?

 

[Operaghost]

Hey there Tim,

Take a look at the front of the ENBT module and the ENET module. The ENBT module says EtherNet/IP whereas the ENET just says Ethernet.

The EtherNet/IP protocol was released after the ENET module was produced. The ENET module only recognizes an older protocol that the PLC-5 and SLC 500 also supported. The PLC and SLC later had versions that did support EtherNet/IP, but the ENET was instead replaced by the ENBT so it never supported EtherNet/IP.

You will need to use the Ethernet devices driver in RSLinx.

OG

 

[Ken Roach]

The "EtherNet/IP" driver discovers devices on its local network by sending out a broadcast packet with the command "List Identity". Every device that gets that request responds with its Identity Object information, which RSLinx checks against its EDS database and can then display in the network browse.

The 1756-ENET, even in the later Series B firmware, never supported that command. I don't know why.

The "Ethernet Devices" driver knows the IP addresses of all the things you want it to communicate with, so it just makes an ordinary direct TCP connection to the device and sends it a non-broadcast version of the "List Identity" command.

This is also often an issue when there are routers or VPN tunnels between your PC and the automation system, which won't forward broadcast packets. I'm online with a system on the other side of the Atlantic right now but have to use the Ethernet Devices driver for that very reason, even with Studio 5000 v34 and FactoryTalk Linx.

 

[joseph_e2]

Another wrinkle is that our IT settings must block some/all of the broadcast packets. I've gotten so used to "inconsistent" results with the Ethernet/IP driver that I never use it anymore and just go directly to the Ethernet Devices driver. If I don't know the IP address of the device, I might try the /IP driver, but will usually end up using Nmap to ping scan if I know the subnet or Wireshark if I don't.

 

[TheWaterboy]

'IT' should leave ports 2222 and 44818 alone on your PLC network.

 

[Tim Ganz]

'IT' should leave ports 2222 and 44818 alone on your PLC network.

What are these ports related to?

 

[Tim Ganz]

The "EtherNet/IP" driver discovers devices on its local network by sending out a broadcast packet with the command "List Identity". Every device that gets that request responds with its Identity Object information, which RSLinx checks against its EDS database and can then display in the network browse.

The 1756-ENET, even in the later Series B firmware, never supported that command. I don't know why.

The "Ethernet Devices" driver knows the IP addresses of all the things you want it to communicate with, so it just makes an ordinary direct TCP connection to the device and sends it a non-broadcast version of the "List Identity" command.

This is also often an issue when there are routers or VPN tunnels between your PC and the automation system, which won't forward broadcast packets. I'm online with a system on the other side of the Atlantic right now but have to use the Ethernet Devices driver for that very reason, even with Studio 5000 v34 and FactoryTalk Linx.

That lines up with what I am seeing.

 

[Tim Ganz]

Hey there Tim,

Take a look at the front of the ENBT module and the ENET module. The ENBT module says EtherNet/IP whereas the ENET just says Ethernet.

The EtherNet/IP protocol was released after the ENET module was produced. The ENET module only recognizes an older protocol that the PLC-5 and SLC 500 also supported. The PLC and SLC later had versions that did support EtherNet/IP, but the ENET was instead replaced by the ENBT so it never supported EtherNet/IP.

You will need to use the Ethernet devices driver in RSLinx.

OG

What was this older protocol for PLC5 and SLC 500? I have SLC 5/05 that I think is Ethernet/IP though?

 

[TheWaterboy]

port 2222 is PCCC traffic for the older PLCs and 44818 is CIP for the newer ones. IT often gets overzealous and will block them between segments that need them. Less of a problem if all are on the same segment but worth knowing about.

 

[joseph_e2]

Sadly, whatever they're doing blocks those packets even when I'm directly connected to the device with a patch cable. Makes things tough.

 

[TheWaterboy]

perhaps windows firewall on your laptop- can you turn it off?

 

[joseph_e2]

perhaps windows firewall on your laptop- can you turn it off?

Not enough to matter. We have Symantec Endpoint running as well. We can turn some of it off but it's always doing stuff. And they also use group policies for a lot of things.

 

[TheWaterboy]

You should convince them to leave those 2 ports alone, It shouldn't be a hard sell. Good luck.

 

[Operaghost]

What was this older protocol for PLC5 and SLC 500? I have SLC 5/05 that I think is Ethernet/IP though?

The older controllers used the CSP protocol. There was a point where the PLC-5 and SLC 500 were upgraded to support both CSP and CIP. CIP is the underlying protocol EtherNet/IP uses. Typically these newer PLCs and SLCs would have Ethernet/IP labeling so you know if they support it or not. And you could use the EtherNet/IP or the Ethernet Devices driver.

But the 1756-ENET was never upgraded. They chose instead to replace it with with a newer module (ENBT).

OG

 

[Ken Roach]

RSLinx intrusion detector !

The "List Identity" command is very simple and easy to detect; just listen on UDP port 44818 for a 24-byte string that begins with 0x64, followed by 23 null bytes.

For kicks I now have a small Linux computer sitting on my automation lab network running Node-Red that will send me a text message every time someone browses the network with the EtherNet/IP driver.

First mistake: if they click Auto-Browse I will get a text every six seconds. Gotta figure out how to limit that, and how to report the IP address of the browsing PC.