To activate 1G LAN, please modify bootloader configuration, steps as below:
1. Press <E> to edit the commands before booting. 
2. Find bootloader config file.
3. Add the parameters ˇ§pci=nomsiˇ¨ in the kernel command line.
4. Excute and reboot to find the connected 1G LAN working porperly .

*It could be set permanently by editting file /boot/grub/grub.cfg.