Why is there a Ethernet Controller boot option in my BIOS?

Question

Why does my BIOS Boot list show Ethernet Controller?

I have disabled it because it slows down the startup time. Why is it still there? How can I boot from it? I am confused.

Answer 1

Its there because some corporate networks support network booting, which means it grabs everything it needs over the network.
This is often done for deployment of machines so you dont need to run around with lots of install disks.

See Wiki's writeup: http://en.wikipedia.org/wiki/Network_booting

Answer 2

You can use your "Ethernet Boot option" to boot linux based systems such as Clonezilla, PartClone, Ubuntu, and a lot of systems and aplications based on Linux PXE(Preboot Execution Environment) without needing to use a Hard Disk on your computer, all the kernel and dependencies will boot up to your RAM from the Ethernet Server, as explanined above:

The Preboot eXecution Environment (PXE, also known as Pre-Execution Environment; sometimes pronounced "pixie") is an environment to boot computers using a network interface independently of data storage devices (like hard disks) or installed operating systems.

The PXE protocol is approximately a combination of DHCP and TFTP, albeit with subtle modifications to both. DHCP is used to locate the appropriate boot server or servers, with TFTP used to download the initial bootstrap program and additional files.

To initiate a PXE bootstrap session the PXE firmware broadcasts a DHCPDISCOVER packet extended with PXE-specific options (extended DHCPDISCOVER) to port 67/UDP (DHCP server port). The PXE options identify the firmware as capable of PXE, but they will be ignored by standard DHCP servers. If the firmware receives DHCPOFFERs from such servers, it may configure itself by requesting one of the offered configurations.

You can find more information about PXE over his specification or even on it oficcial wiki.

You can disable this option on your BIOS if you dont want to use Ethernet boot based systems, actually it would be disabled from factory configurations on most of manufactures.