Assuming your r8168 was compiled correctly, do the following:

1. Create dependency list of kernel modules:

   
   
   

   sudo depmod -a
   
   




2. Add this line to /etc/modprobe.d/blacklist.conf:

   
   
   

    blacklist r8169
   
   




3. Edit /etc/initramfs-tools/modules and add line:

   
   
   

   r8168
   
   




4. Update existing initramfs:

   
   
   

   sudo update-initramfs -v -u -k `uname -r`
   
   

Note that in command 4, those are not quotation marks, but grave accents. That is the key to the left of the one key on the alpha part of the keyboard.

Reboot. You should come up running r8168. To verify, run

sudo lspci -v