将ipv4 netmask转换为cidr格式

2 回答

• 1

  复杂的方法是将网络掩码转换为二进制并计算前导1位的数量 . 但由于只有33个可能的值，更简单的方法只是一个关联数组：

  $netmask_to_cidr = array(
      '255.255.255.255' => 32,
      '255.255.255.254' => 31,
      '255.255.255.252' => 30,
      ...
      '128.0.0.0' => 1,
      '0.0.0.0' => 0);
  

  回复于 2024-04-29T05:48:14+08:00
• 0

  有点坚持主题，但可能会帮助别人，你在这里有解决方案：

  function mask2cidr($mask)
  {
    $long = ip2long($mask);
    $base = ip2long('255.255.255.255');
    return 32-log(($long ^ $base)+1,2);
  
    /* xor-ing will give you the inverse mask,
        log base 2 of that +1 will return the number
        of bits that are off in the mask and subtracting
        from 32 gets you the cidr notation */
  }
  

  PHP ip2long help

  回复于 2024-04-29T05:48:14+08:00