Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a Cisco USB ethernet device plugged in to my 12.04lts. It shows up in lsusb as ASIX Electronics Corp. AX88772 and dmesg notes it:

asix 5-1:1.0: eth1: register 'asix' at usb-000:06:00.0-1 ASIX AX88772 USB 2.0 Ethernet c0:c1:c0:94:f7:bd

(Updating...) I see it listed in /etc/udev/rules.d/70-persistent-net.rules as...

# USB device 0x0b95:0x7720 (usb)
SUBSYSTEM=="net"", ACTION=="add", DRIVERS=="?*", ATTR{address}=="c0:c1:c0:94:f7:bd", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL="eth*", NAME="eth1"

So USB has it, and part of the network system has it, but there is no eth1 in ifconfig and ifup eth1 says

Ignoring unknown interface eth1=eth1

How do I get it working?

share|improve this question
up vote 3 down vote accepted

Go into /etc/network/interfaces and add

auto eth1
iface eth1 inet dhcp
share|improve this answer

I have had a similar problem that required a slightly different solution that I was able to reach thanks to the original poster. I have several Cisco adapters that I am using with embedded systems and so, from time to time, each system will see different adapters. Only one adapter is reliably detected.

What what I can tell, the problem is that each adapter gets it's own line in /etc/udev/rules.d/70-persistent-net.rules which specifies a name for the adapter e.g.

# USB device 0x0b95:0x7720 (usb)
SUBSYSTEM=="net", ..., ATTR{address}=="xx:xx:xx:xx:xx:xx",...,KERNEL=="eth*", NAME="eth1"

# USB device 0x0b95:0x7720 (usb)
SUBSYSTEM=="net", ..., ATTR{address}=="yy:yy:yy:yy:yy:yy",...,KERNEL=="eth*", NAME="eth2"

Only the adapter with NAME="eth1" works happily. Changing the name of all devices to NAME=="eth1" solves the problem. This could be an issue on systems that could use multiple adapters.

Question: Is this the only workaround? It feels very hacky. I should also note that dmesg shows the same message as the original poster always showing eth1 regardless of the udev rules.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

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