Solution for Wired Connection(eth0) not detected in Ubuntu 12.04/Ubuntu 12.10

Some of the latest Laptops especially Dell Inspiron 5420 and Lenovo
G580 series comes with Atheros Network driver which has some problem
with Ubuntu 12.04. The problem is that it will not detect the wired
network connection(eth0) even though wireless connection is working
fine. We can solve this issue by installing the proper network driver.

First you have to download the latest driver from here
http://linuxwireless.org/download/compat-wireless-2.6/

Open Terminal (Alt+Ctrl+T) and extract the downloaded file using
following command.

tar -xvf compat-wireless-2012-07-03-p.tar.bz2

Copy and paste the following commands one by one to change the working
directory and install the driver

cd compat-wireless-2012-07-03-p
scripts/driver-select alx
make
make install
modeprobe alx

Done... Now you should be able to connect to the Internet using wired network.


read more at http://www.zyxware.com/articles/2680/solved-wired-connection-eth0-not-detected-in-ubuntu-12-04