The Fedora 20 installation kernel doesn't support the Intel i218V gigabit controller.
To enable networking under Fedora 20 first install the system without networking.
Next, download an updated e1000e driver.
Place the driver on a memory stick and copy it to the following location on the newly installed system:
/lib/modules/$(uname -r)/kernel/drivers/net/ethernet/intel/e1000e
Finally run the following command:
# depmod -a
Reboot the system and use the ifconfig command to verify that the network interface is active. The yum command can now be used to update the kernel to a version which contains support for the i218V controller:
# yum update kernel*