Disable NAT on RM502Q-AE

IoT Modules 5G Module
1

I bought a Sixfab 5G Modem Kit for Raspberry Pi.
I have a network setup like this:
PC IP address 10.8.9.4;
Virtualized core network Open5gs running on the PC with IP address 10.45.0.x/30;
Sixfab 5G modem with Quectel RM502Q-AE module;
Raspberry pi 4 connected with USB to the 5G modem.
The raspberry network interface (eth1) is assigned an address 192.168.225.X/16.
The modem is configured to be connected to the virtualized network, I can only access it through minicom and AT commands.
How can I disable the internal NAT of the modem so that I can assign the core network address directly to the Raspberry? I need to perform tests between the PC and Raspberry (iperf3 UPD and TCP) and I would need an IP address directly reachable from the PC.

2

You need to switch the operating mode from ECM to MBIM or QMI.

3

Dear @Federico_Baiamonte
We don’t have AT command to disable NAT.
You can try to make the devices in one LAN via router.

4

Yesterday, I switched the modem’s operating mode to QMI. The modem successfully connects to the core network and receives the IP address 10.45.0.2, but the Raspberry Pi is not assigned an IP address via wwan0.

Here’s what I tried:

  1. Switched the interface to wwan0
  2. Ran sudo udhcpc -i wwan0, but no IP address was assigned to the Raspberry, and the internet connection doesn’t start.
  3. The modem seems to be registered and online, but the passthrough to the Raspberry is not working.

Could you please provide:

  1. The correct sequence of commands to configure QMI mode and enable **IP Passthrough.
  2. Any additional configuration files or routing rules that need to be applied.
  3. Any logs or diagnostics I should collect to help troubleshoot this issue.

Thanks for your help!

5

The connection procedure is not Quectel specific.
See How to set up a simple data conne... | FAQ | Support | Techship

You can probably find similar instructions for QMI, but you could just charge the mode on the modem.

6

Dear @Federico_Baiamonte
Please confirm if wwan0 have IP address.
ifconfig wwan0

7

I resolved the issue by using a Docker container. I established an OpenVPN tunnel between the PC and the Raspberry Pi. The OpenVPN server runs on the PC, and I generated the necessary certificates for both the Raspberry and the PC before initiating the connection. The modem operates in ECM mode. This setup resulted in a slight latency increase of about 1–2 ms. The connection is secured and maintained through Open5GS and the srsRAN project.