root@OpenWrt:~# picocom /dev/ttyUSB0 -b 115200
picocom v3.1
port is : /dev/ttyUSB0
flowcontrol : none
baudrate is : 115200
parity is : none
databits are : 8
stopbits are : 1
escape is : C-a
local echo is : no
noinit is : no
noreset is : no
hangup is : no
nolock is : no
send_cmd is : sz -vv
receive_cmd is : rz -vv -E
imap is :
omap is :
emap is : crcrlf,delbs,
logfile is : none
initstring : none
exit_after is : not set
exit is : no
!! Settings mismatch !! Type [C-a] [C-v] to see actual port settings
Type [C-a] [C-h] to see available commands
Terminal ready
AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","","0.0.0.0",0,0
OK
AT+CGPADDR
+CGPADDR: 1,100.125.1.45,42.2.24.8.0.3.5.251.0.0.0.0.0.0.0.1
OK
Your modem has both IPv4 and IPv6 addresses assigned/obtained, so technically it is connected.
At the same time I would configure the proper APN either manually or through the modem GUI.
For manual configuration: AT+CGDCONT=1,"IPV4V6","APN name"
Please validate your configuration against the wiki: https://openwrt.org/docs/guide-user/network/wan/wwan/ethernetoverusb_rndis
I suppose default is wrong, you probably misread the instructions.
It looks like you cannot change the active context, so you can send AT+CFUN=4 before and AT+CFUN=1 after the change.
Do you see usb0 as up and properly configured?
Run ifconfig usb0 and share the result. (ifconfig is obsolete and I should not advise using it).
Then I would check what configuration options are available on the modem itself, for example, the Dial-up Settings noticed on the screenshot above.
Generally speaking, everything looks good already. The modem has IPs from the carrier, router has IP from the modem. Do you see 192.168.225.1 as your default gateway? (run ip r)
ip r
default via 192.168.225.1 dev usb0 src 192.168.225.170
192.168.1.0/24 dev br-lan scope link src 192.168.1.1
192.168.225.0/24 dev usb0 scope link src 192.168.225.170
Well, then the only option I see is to switch from RNDIS to QMI (and lose the modem web interface).
I don't think the process was ever described here in details, so I'll probably need to write some sort of the step-by-step guide.
Please check something while the modem is still in RNDIS mode:
Initially all the changes will be temporary and active until the next reboot.
adb shell
usb_composition 9025 n n y
exit ; only if adb session is not closed automatically
Check with cat /sys/kernel/debug/usb/devices and look for Driver=qmi_wwan
If QMI interface is there, add a new modem id to the serial driver: echo "05c6 9025 ff" > /sys/bus/usb-serial/drivers/option1/new_id
Check with cat /sys/kernel/debug/usb/devices and look for Driver=option
Once the interface is added through Luci, edit the network config file and add option dhcp '0' to this interface. Restart the interface from Luci when done.
If connection is established, all the changes can be made on a permanent basis. In case of failure check the System Log from the moment the QMI interface was added or restarted.