Question

Hello,

We have a modbus device running in a LAN:

localIP: 192.168.1.21
port: 502

It is connected with a GSM router [RUT955] and no physical WAN connection. We would like to add some authentication to this connection. Therefore we would like to forward+tunnel this to our local Ubuntu server.

Let's say for example out ubuntu server has the following IP address:

128.154.26.11

What would be a solution to access the modbus device from 128.154.26.11:5002 with authentication?

Answer 1

Hi,

Could you draw a simple sketch of your network topology? Describe how everything is connected (IP,gateway, subnet) and describe what and from where you want to reach.

Comments

Hello Anonymouse,

I have a device connected to a RUT955.
The RUT955 has a 4G connection to the internet.
My Ubuntu Server is connected to the internet as well.
The Ubuntu Server has a fixed IP adress.
The RUT955 does not have a fixed IP adress.

I would like:

1. Access to the Modbus TCP device from a client connected to the ubuntu server.
2. Have some sort of authentication (client/server)

The RMS forwarding functionality would be perfect but it does not support raw TCP connections.

---

Ok, for this case you need to create one of VPN server in your ubuntu. Router support these: OpenVPN, IPsec, GRE Tunnel, PPTP, L2TP, STunnel, SSTP.

Some examples are here:

https://wiki.teltonika.lt/view/RUT955_Configuration_Examples#VPN