What is the purpose of usb0 ethernet device on Centos 6.5 machine?

Question

My Centos 6.5 machine installed with 2 ethernet device (eth0 and eth1). But when I listed all ethernet device with ifconfig -a as root, in resulted list have another ethernet device usb0, as follow:

usb0  Link encap:Ethernet  HWaddr 36:40:B5:87:34:8C
      inet addr:169.254.95.120  Bcast:169.254.255.255  Mask:255.255.0.0
      inet6 addr: fe80::3440:b5ff:fe87:348c/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:1716 errors:0 dropped:0 overruns:0 frame:0
      TX packets:1314 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000
      RX bytes:238284 (232.6 KiB)  TX bytes:230702 (225.2 KiB)

AFAIK, I never configure it. My Question is, What are the purpose of usb0 ethernet device on my machine?

Answer 1

Basically, it's for TCP/IP communications over USB. Why you would want to do this varies, but usually it's because a specific device requires it. Some notable examples are the BeagleBone, USB tethering with modern Linux kernel based phones, and possibly some amateur radio devices utilizing USB (likely for packet radio).

To the best of my knowledge, usb0 is enabled and configured automatically on many Linux distros.

Answer 2

This is an In-Band management port. IBM, among others, use a lights-out management port. On the back of the machine, it may be called IMM or Service, with a normal ethernet port there. That goes to a small, single-board computer that manages power, serial console, etc. There's a small web server embedded.

The usb0 interface on the is ethernet-over-USB from the IMM to the host. This way, the host OS can contact the IMM and perform configuration and/or management.