Linux – the meaning of entries when running ‘ifconfig -a’

google-chrome-oslinuxnetworkingUbuntuwireless-networking

When I run ifconfig -a on my Chromebook (both through shell inside ChromeOS and my Ubuntu chroot) I get the following entries:

acrbr0: ...
lo: ... 
veth_android: ...
wlan0: ...

I was able to find information about wlan0 and veth_android but not about the others. I don't really know much about networking so I would really appreciate some run down.

Best Answer

The entries you see ae called Predictable Network Interface Names. It means that non-permanent network interfaces (ie, USB interfaces) have a name in the form of enx<MAC_ADDR> or wlx<MAC_ACCR> (or similar), so that any scripts and systems depending on that specific device will have 100% confidence that it's targeting the right device.

The Predictable Network interface naming convention goes like this :

  • Names incorporating Firmware/BIOS provided index numbers for on-board devices (example: eno1)
  • Names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (example: ens1)
  • Names incorporating physical/geographical location of the connector of the hardware (example: enp2s0)
  • Names incorporating the interfaces's MAC address (example: enx78e7d1ea46da)
  • Classic, unpredictable kernel-native ethX naming (example: eth0)

Coming to specific entries you asked for in question, I think potatoman answered it well.

lo : Loopback interface

It's a virtual network interface that your computer uses to communicate with itself. It is used mainly for diagnostics and troubleshooting, and to connect to servers running on the local machine.

wlan0 : Wireless LAN interface

wlan0 is basically your wifi card. It is wireless lan and 0 is the number of your card. The count starts from 0 and goes up (0,1,2,3,etc..). So if you had 2 wifi cards plugged in they would be represented by wlan0 and wlan1.

veth_android & acrbr0 : Net namespaces for Android Containers

acrbr0 is the isolated network interface that gets an IP Address from veth_android ( a virtual ethernet interface for Android ). They are closely related to each other. See the image below (from Page 7 in this link)to get an idea

Net Namespaces in Android Network

Feel free to add details.

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