def next_ip(arg)
      octets = arg.split(/\./, 4).map(&:to_i)
      octets[3] += 1
      raise "out of ips!" if octets[3] > 255
      return octets.map(&:to_s).join(".")
    end
def next_ip(arg)
      octets = arg.split(/\./, 4).map(&:to_i)
      octets[3] += 1
      raise "out of ips!" if octets[3] > 255
      return octets.map(&:to_s).join(".")
    end
Gets the next unallocated IP, given an IP to start with.