Subnet Routing SNAP-PAC S2

Dear forum members,

i have the following issue to deal with:

The business I’m serving uses SNAP-PAC S2 Controller. The only Interface that is used is ENET1 within the automation network. There are also SNAP-PAC EB1 brians used in the same network.

Is it possible to create a second network, using ENET2 so that all the EB1-brains can communicate in the subnet while the PAC S2 Controller functions as a router? So that we are able to monitor the subnet from the superior automation network, which is connected on ENET1 Interface?

However, I was not able to clarify my issue via the controller’s manuals or OPTO’s network documentary. I only found out, that there is no way to reach the subnet on ENET2 via automation network on ENET1.

Could it help to register the IP-address of ENET1 as the gateway-address of ENET2?

If it’s not possible, does anyone have experienced creating some kind of “bypass” in form of a additional router, that is connected either to automation network and subnet?
Primary this configuration shall offer monitoring possibilities.

Greetings from Germany, Holger

Hello LW_Holger,

Welcome to the OptoForums! I’m sorry you did not find your answers in the manuals. This networking guide might be helpful to you, did you find that form 1796?

However, I’d like more information on exactly what you’re trying to connect here, because I think you may already have what you need. What is this other network you mention, and what software will be running on that?

I ask because it sounds like you’ll want to put those EB1 brains on the second network (that is actually the recommended topology in many cases, ENET1 for the higher-level software/office network and ENET2 for connecting to your real-world devices and sensors).

All you need to do is change the IP addresses of those brains in your SNAP-PAC-S2’s strategy to match the new network. The SNAP-PAC-S2 knows how to communicate to those brains via the second network and how to communicate with software/HMIs etc. on ENET1 so there’s no need for any kind of bypass.

The software/HMI etc. communicating to the SNAP-PAC-S2 will ask for values from those EB1’s by tag name and the SNAP-PAC-S2 will read (or write) to the appropriate brain.

I’ve made a few assumptions here and glossed over a few details, so I hope you’ll share more about the pieces you’re trying to connect so we can better help you.


Hello Mary,

thank you for your post. Indeed, there are a lot Information I missed reading. I was looking for the following part I found in the networking guide:

“SNAP PACs and groov Boxes are not routers, because they do not provide routing or address
translation, but their separate interfaces work like a router’s Interfaces.”

So it is impossible to get access to the ENET2 network from the ENET1 Network (e.g. using a SNAP-PAC-S2 Controller).

Best regards,


There’s a little more to the story. While all you quoted is true, you still have the ability to write some code in the SNAP PAC. See this discussion: SNAP-PAC-EB1 Install Firmware via Ethernet Passthrough Connection

But I’m still interested in hearing about your “big picture”: the what you’re trying to connect and the why of what you’re asking to do here?

Thank you for the Information. I also found that topic you’ve posted. It’s not about configuring I/O devices, it’s just about how to access to the subnet, in which the I/O devices are located. We try to create a solution to monitor the subnet traffic in a 172.x.x.x subnetwork from a superior 192.x.x.x network, not using PAC-Software but monitoring software.

As far as i read OPTO’s documentary, the only way to get access to the subnet is using PAC-Software (e.g. Inspect the Controller). So there is no way, that a monitoring-device in the superior 192.x.x.x network is able to get access to the subnetwork 172.x.x.x, using PAC-S2-Controller as a router.

You need to install an additional router, that “bypasses” the PAC-S2 Controller for instance.

We are interested in monitoring data packages transmitted either in the subnet and in the superior network. As we are using PAC-S2-Controller, it’s like a “barrier” to the subnet. So it’s impossible to measure data traffic in the subnet. Another solution would be, to install two monitoring devices, either for the superior Network and the subnet. But that is not an option, we rather would like to go the “routing”-way :slight_smile:

I hope I presented my requset properly.

Best regards,