SIMCOM7600 Limiting external connection
aleksander at aleksander.es
Mon Aug 30 11:57:40 UTC 2021
Bon dia Aaron,
> I have an issue when I want to connect to an embedded device with SSH
> through VPN. It's strange because, depending on the type of SIM (M2M or
> conventional SIM), the module (SIMCOM 7500 or 7600) and the driver (qmi or
> the one from simcom) it works or not.
When you refer to the driver from simcom, is that a qmi_wwan driver
variant? Or a GobiNet driver variant?
> The cases are:
> - Using a M2M SIM and either qmicli/simcom drivers:
> - Both modules (7500E and 7600G-H) work properly (embedded has
> Internet connection, and I can connect to it through SSH using the VPN.
> - With this SIM, the wwan0 interface has an IP 10.128.X.X.
> - Using a "conventional" SIM:
> - With the simcom driver, both modules work well (Internet + VPN).
> - With the qmicli, 7500E works well, but the 7600G-H only has
> Internet connection (VPN doesn't work).
> - With this SIM, the wwan0 interface has an IP 172.19.X.X.
You get the same kind of IP address both when using the simcom driver (with
AT commands) and the upstream one (with qmicli), right?
> When using qmicli I execute the following lines (using qmicli 1.16.2):
> 1. qmicli -d /dev/cdc-wdm0 --dms-set-operating-mode='online'
> 2. ip link set wwan0 down
> 3. echo 'Y' | tee /sys/class/net/wwan0/qmi/raw_ip
> 4. ip link set wwan0 up
> 5. qmicli -p -d /dev/cdc-wdm0
> --device-open-net='net-raw-ip|net-no-qos-header' --wds-start-network="apn='PROVIDER',ip-type=4" --client-no-release-cid
> 6. udhcpc -i wwan0
> 7. ifmetric wwan0 500
> When using simcom driver, I use raw AT commands + dhclient.
> To sum up, it only fails the external SSH connection when using
> "conventional" SIM + 7600 + qmicli, so I guess it has to do with their
> configuration or something related.
It's a bit strange, not sure what to say. Could it be something related to
using raw-ip in the 7600? I think 802.3 is not supported when using QMI in
such a new module. Have you tried contacting simcom support and explaining
the problem? Not sure what kind of support they give for
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