def cidr_to_netmask(cidr_range)
      cidr = IP::CIDR.new(cidr_range)
      return cidr.ip.ip_address, cidr.long_netmask.ip_address
    end
def cidr_to_netmask(cidr_range)
      cidr = IP::CIDR.new(cidr_range)
      return cidr.ip.ip_address, cidr.long_netmask.ip_address
    end
converts CIDR to ip/netmask

 === Parameters
 cidr_range(String):: target range in CIDR notation
 === Return
 result(Array):: array which contains ip address and netmask