Cross Subnet Comms

Hi,

I have a local network, lets say 192.168.1.xxx, on this network I have my local devices, HMI, PLC, Drives etc.

I have a data collection network which lets say is on 1.1.1.xxx, PC sits on this network and requires to pull data from the PLC.

And then I have another network which pulls data, which is on 1.2.3.xxx

I require the PLC to communicate with each network and vice versa, I have an AB PLC with one Ethernet card, so I was wondering if using a Router is the best solution here?

Note - Its a Rockwell PLC, I've seen Allen Bradley 1783-NATR device.

Jackllx said:

...I was wondering if using a Router is the best solution here?...

Click to expand...

I am pretty sure a router your only* standard solution, at least if you intend to run communications through the network interfaces with those IP addresses.

The -NATR, if used, would be acting as a layer of de facto routing.

What is the physical layout? Does the 192.168.1.0/24 network connect to the outside world? Pushing data from the PLC on that network might be the simplest solution, rather than pulling from the non-PLC hosts.

Security is a whole 'nother kettle of fish.

* you could also add a second network interface to the non-PLC hosts and connect those interfaces to the 192.168.1.0/24 network, if the geography makes that feasible; there is still routing involved, but it would be handled more or less automatically.

...

drbitboy said:

I am pretty sure a router your only* standard solution, at least if you intend to run communications through the network interfaces with those IP addresses

Click to expand...

My exact thought as I read the OP's post.

And opening a PLC up to three networks is a potential security concern. But that wasn't the question that was asked.

OG

You could use 3 network cards

Router it is, thanks.

For cheap DIY router I've been using the 4 gigabit port Protectli boxes off of Amazon. Loaded with opnsense (all webgui configuration), which is a free distribution.


OPNSense is super powerful and featureful. I've done odd things like have multiple VLANs going out to a managed switch with each port being it's own subnet and DHCP pool. The router easily routes (or blocks) between subnets.


You can also setup OpenVPN, or wireguard to manage remotely anything attached to the router.