Problem trying to use a USB modem

[Patrick9876]

RT-AC86U running Merlin 386.1.2
I have no trouble using a cell phone as backup WAN connection. The router detects it as an Android device and the log shows it connecting as an RNDIS device.

Several days ago I bought a USB LTE modem - an Inseego (formally Novatel) USN800 - to use on a laptop (running Windows) in areas with weak cell signals. Both the modem and the phone work fine (when the cell signal is strong enough) on the laptop. Both use the Windows generic Remote NDIS
driver.

I decided to try the modem as a backup on my router and have had no luck. Here's a short excerpt from the router's log

Apr  7 13:59:50 kernel: usb 3-1: new high-speed USB device number 53 using ehci-platform
Apr  7 14:00:10 kernel: usb 3-1: USB disconnect, device number 53
Apr  7 14:00:10 kernel: usb 3-1: new high-speed USB device number 54 using ehci-platform
Apr  7 14:00:10 kernel: cdc_ether 3-1:1.0 eth7: register 'cdc_ether' at usb-ehci-platform.0-1, CDC Ethernet Device, 00:15:ff:04:84:95
Apr  7 14:00:10 hotplug: add net eth7.
Apr  7 14:00:11 hotplug: set net eth7.
Apr  7 14:00:30 kernel: usb 3-1: USB disconnect, device number 54
Apr  7 14:00:30 kernel: cdc_ether 3-1:1.0 eth7: unregister 'cdc_ether' usb-ehci-platform.0-1, CDC Ethernet Device
Apr  7 14:00:30 hotplug: remove net eth7.
Apr  7 14:00:31 kernel: usb 3-1: new high-speed USB device number 55 using ehci-platform
Apr  7 14:00:51 kernel: usb 3-1: USB disconnect, device number 55
Apr  7 14:00:51 kernel: usb 3-1: new high-speed USB device number 56 using ehci-platform
Apr  7 14:00:51 kernel: cdc_ether 3-1:1.0 eth7: register 'cdc_ether' at usb-ehci-platform.0-1, CDC Ethernet Device, 00:15:ff:04:84:95
Apr  7 14:00:51 hotplug: add net eth7.
Apr  7 14:00:52 hotplug: set net eth7.
Apr  7 14:01:11 kernel: usb 3-1: USB disconnect, device number 56

While this is happening the router's Network Map shows the USB connection (USB 2.0 in this case) switching between "No Device" and showing a "Novatel USB 800" ... with the "No Device" predominating.

On the other hand, when I connect my phone the log shows:

Apr  7 14:04:44 kernel: usb 3-1: new high-speed USB device number 62 using ehci-platform
Apr  7 14:04:44 kernel: rndis_host 3-1:1.0 usb0: register 'rndis_host' at usb-ehci-platform.0-1, RNDIS device, 02:56:05:04:38:39
Apr  7 14:04:44 hotplug: add net usb0.
Apr  7 14:04:44 hotplug: Got net usb0, vid 0x1bbb, pid 0xf00e.
Apr  7 14:04:47 hotplug: set net usb0.

In the router's USB Modem / USB Tethering panel, the Novatel USB 800 is not listed in the USB Adapter list. Does this mean I'm just plain out of luck, or is there something else I can try? I can obviously use my phone if I lose my internet connection (Comcast cable), but I'd rather not tie up my phone if I don't have to.

 

[YoshiT]

Your issue may be related to below post, though my phone was never recognized as eth7.
=> https://www.snbforums.com/threads/u...-2021-potentially-revvl-5g.71533/#post-680325

 

[Patrick9876]

I think my problem is possibly different from YoshiT's, but I can't get even his basic diagnostic commands (from the thread he referred to) to work. He suggested issuing

cat /proc/bus/usb/devices

but I have only /proc/bus/pci in my router - no /proc/bus/usb directory at all. YoshiT suggested that maybe the difference was between my AC86U and his AC68U but I suspect the difference lies somewhere else ... aided and abetted by my ignorance of Linux.

Is collecting this device information a profitable path to go down, or am I beating a dead horse?