private function getIPAddressRangeAsInts()
    {
        list($start_ip, $end_ip) = $this->getIPAddressRange();
        $start_ip = ip2long($start_ip);
        $end_ip   = ip2long($end_ip);

        if ($start_ip === false || $end_ip === false) {
            throw new \RuntimeException('IP address range calculation failed: ' . print_r($this->getIPAddressRange(), true));
        }

        return [$start_ip, $end_ip];
    }