private function getAddressRange($netblock)
    {
        $t = explode('/', $netblock);
        $addr = $t[0];
        $cidr = $t[1];

        $corr=( pow(2, 32) - 1)-(pow(2, 32 - $cidr) - 1 );
        $first=ip2long($addr) & ($corr);
        $length=pow(2, 32 - $cidr) - 1;

        return [
            'begin'  => $first,
            'end'   => $first + $length,
        ];

    }