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I have about 50 industrial machines (mostly CNC controlled by a PLC). They have ethernet jacks, with an existing IP address set. I need to connect them to the main building's network (which uses an entirely different IP scheme). I have accomplished this with a few machines by installing an industrial router in the machine, and using the router's NAT to bridge the two networks. It works well, but requires a router that costs around $400, requires an electrician to install, and requires downtime on the machine.

However, each of these machines has a Samsung Galaxy Tab A8 or Samsung Active Pro tablet mounted to it, connected to the building's WiFi. I have full control over the tablets, I can root them if needed.

I am wondering if I attach an ethernet adapter to the tablet's USB-C port (I've found a few that have pass-thru charging), then plug the ethernet cable into the CNC/PLC if there is a way I can bridge the wireless connection, and also have some NAT to do the address translation and forward the needed ports.

Changing IP addresses on the machine is not an option, and altering the building's network is not an option.

I have no need for DHCP, and only a couple of devices are on the ethernet side.

Has anyone done this?

Additional info:

I am fully aware that wiring each machine would be ideal, but it is not feasible. To show why, I’m putting some numbers below. This application is theoretical at this point, we have a small amount of data we want to relay to an on-site server, which is then parsed and displayed on the tablets. If the testing works, we’d look into customized android powered hardware in place of the tablets.

50 machines total (at this site) $2,000 per minute downtime

30 minutes required to install cable (remove guarding and wire covers, run through tracks, replace covers)

$60,000 downtime (30 min x $2,000) $250 per cable to run $2,500 two engineers to review changes to networking and resign/recertify safety)

$62,750 / machine $3,137,500 / site

So they can spend 3 million per location and risk angry customers from downtime or they can relay some data via some android tablets.

The data is not mission critical, it is used to monitor efficiency. If there are network issues the worst that happens is the data is reported when the connection is restored.

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Honestly, I don't think using the tablets as routers is a very good way to do this due to the complexity and you essentially having dozens of tiny networks interconnected for no advantage. Why can't you just use VLAN's in the network and build one interconnecting route? This sounds like a basic network setup question.

Basically in your primary router for your network (usually, could be the switch as well) you would build a second "CNC" VLAN that matches the IP scheme of the CNC machines, and you assign switch ports to connect them to the network on the correct CNC VLAN. Then the router would just allow the two networks to communicate via the primary gateway (the router) for each network.

This is a very common setup actually. How exactly it would be implemented would vary a lot based on your equipment. This could be done via dedicated hardware (like one switch just for the CNC equipment) or by assigning ports of an existing switch to be untagged into the CNC VLAN.

This would allow for minimal new equipment and simple network routing, and minimal complexity while maintaining network security... Which is preferred in network setup.

I think adding additional routers or using the tablets/phones connected to each device as a routing device would add a level of complexity that would be quite a headache, especially later on.

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  • I could see this being a normal setup if there were a few machines but we are talking about 50 machines using identical ip addresses, needing access to the same port ranges (some of which span hundreds of ports). As an example I have 50 machines, all with an ip address of 192.168.1.1, needing ports 100-350 accessible. This would also require cables be run to each machine which is a cost greater than $10,000 per facility. It’s not a practical solution.
    – Developer Gee
    Commented Nov 26, 2022 at 16:38
  • It would have to be easier to just re-IP the equipment...
    – acejavelin
    Commented Nov 27, 2022 at 22:05
  • No it wouldn't, this is industrial equipment with dozens of devices connected to it via ethernet controlling moving parts and critical safety equipment, not to mention it requires specialized software that is expensive. Making changes to anything safety related requires a thorough review process and multiple engineers to validate the changes. This would have to be done 50 times over (once per machine, even though they are identical). This isn't just PCs in an office. Downtime also costs more than $2,000 / minute
    – Developer Gee
    Commented Nov 28, 2022 at 14:16
  • No offense, but I can't image the manufacturer of that equipment doesn't have a solution for this. Although this sounds like a massive undertaking, if done correctly this would only need to be done once and would rectify the problem, and if equipment was properly installed into the network at initial installation or replacement, this entire situation should be mitigated permanently. You might not like my answer, but it is technically correct and the proper way it should be done. This will continue to be an issue until it is handled properly and with a permanent fix, and the cost will only rise
    – acejavelin
    Commented Nov 28, 2022 at 15:09
  • The manufacturers of the equipment do not have a solution. “No offense” but I don’t think you have an understanding of how the world of industrial engineering works. Most equipment is custom built for manufacturers. There’s not really an “I want to add a second network card option”. You call them 6 months after they made it and they say “sorry we don’t remember how that machine works”. Also as I said before, this would not be done once, this would be done in several facilities.
    – Developer Gee
    Commented Nov 30, 2022 at 0:27
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Because I posted a simple question, I will post the simple answer I have found.

The answer to the question is yes, Android tablets can work as an access point when combined with a usb ethernet adapter.

They must be rooted in order for it to work, once rooted, the nat/port forwarding can be managed from iptables.

How well it performs obviously depends on the existing wifi network, the quality of the tablet, the number of devices connected, and the amount of network traffic.

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