Cat 6 is preferred if you're working near the long limit of the cable, it's Shielded Twisted Pair cable certified for Gigabit networks. Cat 5e is category 5 Unshielded Twisted Pair with tighter twist and a little better signal quality, good for 30 to 100 meter runs on 100BaseTX networks. Cat 5 is fine for short (25 meters or less) 100BaseTX runs and patch cords, and a little cheaper than Cat 5e. Cat 3 cable is adequate for between the router and the broadband appliance; the fastest private broadband is 5 or 6 Mb/sec and Cat 3 is certified for 10BaseT...