parameter specifies where data goes if it doesnt match any of the IP ranges.
This could be /dev/null depending on your aims.
-i input parameter gives the file to take input from (default standard input).
-f file parameter must be given before the list of IP addresses.
spec parameter is the IP addresses that go to the file in question. It is of the
start[-end][:start[-end]] where start and end specify the start and ends of ranges of IPs. Also the
CIDR notation can be used or a single IP address.
If there is a large number of IP ranges then a file name can be given which
contains a set of IP ranges, one range per line.