I'm new so appologies if this is the wrong forum. I wanted to share a solution for this issue as I've been searching for days to fix it.
ubuntu 12.04 and its kernel 3.2.0-23 is not compatible with the RTL8101E/RTL8102E PCI Express Fast Ethernet controller
When booting from the live CD wired connection fails, even after the MAC is set (its blank by default)
The issue is with the default module r8169.ko used by the kernel, it needs to be blacklisted.
sudo gedit /etc/modprobe.d/blacklist-network
then add a line to the file
The correct driver/module is on the realtek site called r8101, but the source code won't compile on the new kernel.
I found this link which has the source and patch which can be applied to it to allow it to compile on the new kernel and produce the r8101.ko file.
Once the r8101.ko file is made the script fails to install it so next copy it to;
Then I installed it using these commands
sudo depmod -a
sudo modprobe r8101
The last step is to fix the missing MAC address and restart network manager using these commands, you can use any MAC you like, don't have to use 00:28:C7:0A:42:A2
sudo service network-manager stop
sudo ifconfig eth0 down
sudo ifconfig eth0 hw ether 00:28:C7:0A:42:A2
sudo ifconfig eth0 up
sudo service network-manager start
Then plug in the network cable and away we go