Why do I have to extend my Ethernet?
For a full explanation let's get Physical (#engineerjoke). First, the Ethernet Physical Layer - in plain English how we actually send signals over copper wires - works by sending really, really fast pulses of + 2.5 and - 2.5 volts of electricity. When the volts are HIGH (2.5 volts) we call it a 1. When the volts are LOW (-2.5 volts) we call it a 0. Thus a bit of binary is born!
Ah the magic of logic. And boys and girls, when a 1 and 0 get together and love each other very much, 8 times to be exact, we call it a byte .
But . . . even the best wires in the world have some resistance. What starts out in the beginning as 2.5 volts wears away as it trudges down the copper wires of Category cable. Eventually the electrons have gotten so tired they stop being excited at all. We can all blame Georg Simon Ohm for this. He's the one who made Ohm's Law.
To help us deal with our grief our good friends at IEEE (pronounced I - triple - EEE) set a standard that, as long as you're on CAT 5 or higher cable, your network device has to at least send and receive signals that can travel 100 m (330 ft). So, that's what we all do.
For my detail oriented friends, yes, of course some brave souls have made their switches or cables to go further than the minimum. But, like all good standardized testing situations, if you can just do the minimum, why wouldn't you?