The "used" IP addresses in a network will be the DHCP pool (if the network is running a DHCP server) + all the statically assigned IP addresses on the network. If you don't have that information available for your network, then unless it's a small network, you've got a mess on your hands.
The information on Computing.Net is the opinions of its users. Such
opinions may not be accurate and they are to be used at your own risk.
Computing.Net cannot verify the validity of the statements made on this
site. Computing.Net and Purch hereby disclaim all responsibility
and liability for the content of Computing.Net and its accuracy.