A lot of modern versions of BIOS have built-in diagnostic tools of network connection. The motherboards by ASUS have special sections “LAN Cable Status” or “AI Net2” for this which can be located in “Advanced” or “Tools”. The diagnostic utility in motherboards by Gigabyte starts using the command “SMART LAN” in the section “Integrated Peripherals”. The similar tools can also be found in motherboards by other manufacturers.
A twisted-pair cable consists of four pairs of wires; the status of each of them will be displayed in Status: Open – a pair is not connected or it has a failure; Normal – the status of a pair is normal and Short – a pair is shorted. A desired cable length in meters is displayed in “Length” before failure or interruption.
The wire pairs 4-5 and 7-8 are not used with the network adapter speed of 10/100 Mbt/s so their status may be defined as Open or Short.
If the value Enabled is set for “POST Check LAN Cable” parameter, the network testing will be implemented during every computer booting. In case of failure, the booting will be stopped and a certain warning will be displayed on the screen. This is useful in those cases when the server availability is necessary for computer operation. Otherwise, it is better to set Disabled for this parameter in order not to increase the booting time.