# File lib/ipaddress/ipv4.rb, line 795
    def subnet(subprefix)
      unless ((@prefix.to_i)..32).include? subprefix
        raise ArgumentError, "New prefix must be between #@prefix and 32"
      end
      Array.new(2**(subprefix-@prefix.to_i)) do |i|
        self.class.parse_u32(network_u32+(i*(2**(32-subprefix))), subprefix)
      end
    end