RSLinx Devicenet Passthrough via VPN

I recently separated the office network from the Plant network with a firewall and my PC is on the office side. I have to VPN into the plant network in order to get to the PLC's (All AB). I have several SLC 5/05's with a devicenet network. I was setup in RSLinx to use the devicenet passthrough driver in order to look at drive parameters form my desk. Since I hooked up the VPN, the passthrough driver won't see any devices on the devicenet network. I can get to the PLC's without any problem. Any idea? I am using RSLinx Classic v. 2.54

Interesting ! I have not seen this before.

What sort of VPN device or software did you use ?

Are you using the RSLinx Classic "Ethernet Devices" or "EtherNet/IP" driver to connect to the SLC-5/05 controllers ?

Check the Default Gateway in the controller's TCP/IP configuration. Is it set to the address of the VPN device ?

I am using a watchgaurd firewall xtm 2 series. I use the Ethernet Devices driver in RSLinx. I have no problem connecting to any of the PLC's. I have the Gateway Address in each of the PLC's set to 0.0.0.0

My first troubleshooting step would be to move a PC to the automation network side and see if I can browse through the RSLinx 1747SDNPT driver to DeviceNet successfully. That will help you narrow down if the VPN is in fact the issue, rather than just a coincidence.

The second thing I'd try is to put the Default Gateway address in the SLC-5/05's to the address of the VPN device. I realize that the VPN device is supposed to make your PC appear like a local node, but I can't be sure that it's not part of the problem.

Ken Roach said:

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The second thing I'd try is to put the Default Gateway address in the SLC-5/05's to the address of the VPN device. I realize that the VPN device is supposed to make your PC appear like a local node, but I can't be sure that it's not part of the problem.

Click to expand...

I'll vote for this. I've run into this exact thing more times than I can count. Local connections are no issue, but things disappear or are intermittent over a VPN connection. Setting the gateway solves the issue.

I am not able to change the gateway right now because the processes are running. However, I took my PC to the plant network side and I could easily configure the devicenet passthrough drivers. Then I put my PC back on the office network with the passthrough drivers still configured. Now I can see the devicenet networks without any problem. Next chance I get, I'll change the gateway to the VPN and see if that takes care of things... Thanks for your help.

Thanks for posting that followup !

The 1747-SDNPT drivers are a little bit complicated. The controller itself is involved (you must cycle Run/Prog/Run after defining the driver) and there's a little bit of DeviceNet data server/helper software that you'll see running in the taskbar next to RSLinx.

My guess is that the controller knows the IP address and maybe something else (like the CIP serial number) about the PC that has the RSLinx 1747SDNPT driver running, and that when the packets are coming from a VPN or gateway device it gets confused.

You probably wouldn't see this with a Logix-family driver that's CIP all the way through.

Funny thing is I didn't cycle the PLC to program after I configured the passthrough drivers. I never really noticed the RSLinx DeviceNet server running in my task bar before. Also, I have DHCP on my laptop, so the IP address changes. Also, the Logix processors were fine from the start. I could drill down through the SDN card without any trouble.