IP and Subnet to Start IP End IP

Question

So I have an IP with a Subnet like: 8.8.8.0/24

How can I convert this to 8.8.8.0 and 8.8.8.255 (actually their ip2long resultants)

In PHP and JavaScript

Answer 1

I will assume you will also need for other mask like 8,16,...

ip="8.8.8.0/24"

1. extract each parts ip_array=ip.match(/(\d+)\.(\d+)\.(\d+)\.(\d+)\/(\d+)/) //js regex

2. convert to number ip_num = (ip[1]<<24)+(ip[2]<<16)+(ip[3]<<8)+(+ip[4]) //# 0x08080800

3. mask=(1<<(32-ip[5]))-1 //# 0xFF

4. ip_num | mask will be 0x080808FF which is 8.8.8.255

5. ip_num & (0xffffffff ^ mask) will be 0x08080800 which is 8.8.8.0

6. you need to convert ip_num back to ip string back

Answer 2

To generate a list of IP addresses from slash notation:

$range = "8.8.8.0/24";
$addresses = array();

@list($ip, $len) = explode('/', $range);

if (($min = ip2long($ip)) !== false) {
  $max = ($min | (1<<(32-$len))-1);
  for ($i = $min; $i < $max; $i++)
    $addresses[] = long2ip($i);
}

var_dump($addresses);

To check if an IP address falls within a range:

$checkip = "8.8.8.154";
$range = "8.8.8.0/24";

@list($ip, $len) = explode('/', $range);

if (($min = ip2long($ip)) !== false && !is_null($len)) {
  $clong = ip2long($checkip);
  $max = ($min | (1<<(32-$len))-1);
  if ($clong > $min && $clong < $max) {
    // ip is in range
  } else {
    // ip is out of range
  }
}