Your ISP remaps your address to its address before sending it on. Then
they can "give" you any address that is not "special" on your side of
the gateway. They will have a gateway for every 20,000 customers or so.
The address you get will not be normally visible to the outside world.
Thus, you do not need to find "free / available" addresses. If you
setup a fully private "subnet", use 192.168.0.* where is individual
computers on your private subnet and 192.168.0.1 is reserved for your
computer that connects to the internet on a different "card / port".
JosephKK
