Killer Ethernet 2400: no wired internet
Solution 1:
I suggest that you update the ethernet driver alx. Download this package to your desktop. Right-click it and select 'Extract Here.'
Then, go to the directory <extracted backport>/drivers/net/ethernet/atheros/alx/ and make changes in files reg.h and main.c as described here.
Now, back to the terminal:
sudo apt-get update
sudo apt-get install linux-headers-generic build-essential
cd ~/Desktop/backports-20151115
make defconfig-alx
make
sudo make install
Reboot and tell us if there is any improvement. We will probably have one more step.