grepcidr can be used to filter a list of IP addresses against one or more
Classless Inter-Domain Routing (CIDR) specifications, or arbitrary networks
specified by an address range. As with grep, there are options to invert
matching and load patterns from a file. grepcidr is capable of comparing
thousands or even millions of IPs to networks with little memory usage
and in reasonable computation time.
Signed-off-by: Adam Vandenberg <flangy@gmail.com>