Hello,
I am working at a research organization where we are using Quectel 5G modules to connect to an in-house M2M 5G network. For our current project we would like to realize latency and speed requirements that prevent using the generic serial (“Option”-compatible) interface, and instead opted for the CDC ECM-compatible interface available via USB, since this interface is widely compatible and well documented. Since our project is based on an embedded platform, we cannot build on networking and USB stacks present in major general purpose operating systems, and instead implemented our own driver on top of an RTOS. This works fine, and we are able to connect to public 4G networks without major issues.
We have noticed that the RM500Q acts as a router in CDC ECM-mode. This is not an issue per se (though it seems unnecessary), but in our setup, the device does not appear to configure outbound routes automatically. This is the output of AT+QETH="routing":
+QETH: route IPv4:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.225.0 0.0.0.0 255.255.255.0 U 0 0 0 bridge0
Notably, outbound routes on the rmnet_data0 are missing here. These routes are configured automatically on a public 4G network we tried, but so far, we couldn’t figure out with our infrastructure partner why routes are not configured automatically on our 5G network.
Therefore, we have tried adding routes on the device using the documented add operation of the AT+QETH="routing" command. However, any invocation of the command (such as the documented example in section 12.7.3. of the commands manual) in any combination (such as with or without quotes on strings) on properly configured PDP contexts results in an ERROR output. We have enabled COMMON-RGMII when it was disabled, although we couldn’t manage to enable IP-passthrough mode.
When using the QMI interface or the QPING command, we can reach hosts on our network without issue. However, presumably due to the missing routes on the device, any packets destined for our network are dropped on the device with a “Destination Net Unreachable” response in CDC ECM-mode.
In case you have a suggestion on why adding routes might fail, I’d be very happy to try this out. If this is possible, we would also like to further troubleshoot this issue via ADB. Would it be possible to unlock ADB access for one of our devices (QADBKEY output is 42003012)?
Thank you for your help 