0

I am trying to attach a network interfaces (Ethernet Port and mobile Broadband) to my Pi through USB. When I do this on my Pi 1 or Pi Zero it shows up and works without a hitch, but with the exact same installation on the same SD card on a Pi 3, the interfaces do not work.

On the Pi 3, they are detected as a USB devices but do not show up when I query using commands like ip and ifconfig, even ifconfig -a.

I noticed that when attempting this on the Pi 3, the output from dmesg lacks the lines containing register 'asix' at usb-xxxx:xx:xx-x.x CDC_Ethernet Device ... (for the USB Etherne)
register 'cdc_ether' at usb-xxxx:xx:xx-x.x CDC_Ethernet Device ... (for the mobile broadband)

If it's relevant, I have removed the Pi 3's Ethernet port in order to slim down its profile.

Why is the same installation behaving differently on different Pis?

  • Paste into the question the output of lsusb when the ethernet dongle is attached. If the command is not found, sudo apt install usbutils. – goldilocks Apr 29 at 22:21
2

It seems for me that you try to use OTG Gadget ether mode. This mode emulates a USB connection as ethernet connection so you can use it like a normal network connection. This only works if the USB port is direct connected to the USB on-board device. Only on a Raspberry Pi Zero and Pi Zero W is it the case. I don't know but it seems also be the case with a Raspberry Pi 1.

A Raspberry Pi 3B has more than one USB port so it uses internal an additional USB hub to split the one USB port from the on-board device. This is the reason why OTG Gadget mode doesn't work with a RPi 3B. It cannot manage a USB hub.

To have a wired ethernet connection with a RPi 3B just use its ethernet port. Btw. this ethernet port is also connected to the USB hub and shares its bandwidth with other connected USB devices.

  • You should be able to use a USB ethernet dongle on any model. Telling someone to just use the eth jack is not really a good answer... – goldilocks Apr 29 at 22:20
  • @goldilocks The question was "Why is the same installation behaving differently on different Pis?". Do you mean the side note isn't a good answer because the other end may not have an ethernet port? Using an USB ethernet dongle is of course a better answer if it was asked ;-). Thanks for the idea. I will update my answer ... – Ingo Apr 29 at 22:35
  • @goldilocks I'm just a bit unsure: where and how do you want to use a USB ethernet dongle in conjunction with a RPi 3B to be used for Gadget mode? – Ingo Apr 29 at 22:43
  • The OP never mentions gadget mode (cdc_ether is not specific to that). Why s/he wants to use a dongle on a board that already has an ethernet jack of course remains a mystery... – goldilocks Apr 30 at 2:40
  • @goldilocks Ah.. now it gets clearer. I misunderstood "attach a network interface (Ethernet Port) to my Pi through USB". I don't read that to use an USB/WiFi dongle. I read that to use an USB connection to emulate ethernet - what's doable with Gadget mode. And with this I confused cdc_ether with g_ether Raspberry Pi Zero OTG Mode. – Ingo Apr 30 at 8:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.