Press the "del" key to enter the bios. Go to the "onboard devices configuration" in the "advanced" section. Find the "onboard PCIE ghz lan" and enable it.
On board Pcie 10/100 M lan [Enabled]
I also c h a n g e d :
Lan Option Rom [Enabled] (previous setting was : Disabled)
At beginning Bios showed : wrong Realtek settings (some similar words) press shift + F10 .
In that way I opened ''Realtek Pci Express Ethernet Boot Agent configuration menu '' .
The new setting is now :
Boot order : Rom Disable
At the screen bottom you read: Network Boot disabled, boot local devices
previous was: Boot Order Pnp/Bev (BBS)
At the screen bottom writes : Boot ordered by BBS Bios, If BBS Bios present
Now I am not more able to press alt + F10 to change again, Bios system boots quickly and does not show any more ''wrong Realtek settings'' (similar).