IP/掩码位来表示一段IP范围，那么怎么通过掩码位计算出对应的子网掩码呢？
基本概念：掩码位即网络地址的位数。例如192.168.11.130/31表示网络地址有31位，主机地址有1位，那么31对应的子网掩码就是255.255.255.254(31个1+0)
计算掩码位，就是得到掩码位的二进制序列，然后每隔8位转换为十进制。
Java的Integer.parseInt可以将指定进制的字符串序列转换为int类型。输入一个掩码位，得到对应的子网掩码的点分十进制表示的代码如下：
for(int i=1;i<32;i++) {
int ip = 0xFFFFFFFF << (32 - i);
String binaryStr = Integer.toBinaryString(ip);
StringBuffer buffer = new StringBuffer();
for(int j=0;j<4;j++) {
int beginIndex = j*8;
buffer.append(Integer.parseInt(binaryStr.substring(beginIndex, beginIndex+8), 2)).append(".");
}
System.out.println("net mask "+i+" ,submask:"+buffer.substring(0,buffer.length()-1));
}上述代码即可输出1-31掩码位对应的子网掩码列表。其中
0xFFFFFFFF << (32 - i)就是得到对应的二进制序列。

IP/掩码位来表示一段IP范围，那么怎么通过掩码位计算出对应的子网掩码呢？
基本概念：掩码位即网络地址的位数。例如192.168.11.130/31表示网络地址有31位，主机地址有1位，那么31对应的子网掩码就是255.255.255.254（31个1+0）
通过移位计算，得到主机最大值，和网络地址最大值，图解原理如下：
计算掩码位，就是得到掩码位的二进制序列，然后每隔8位转换为十进制。
Java的Integer.parseInt可以将指定进制的字符串序列转换为int类型。输入一个掩码位，得到对应的子网掩码的点分十进制表示的代码如下：
for(int i=1;i<32;i++) {
			int ip = 0xFFFFFFFF << (32 - i);
			String binaryStr = Integer.toBinaryString(ip);
			StringBuffer buffer = new StringBuffer();
			for(int j=0;j<4;j++) {
				int beginIndex = j*8;
				buffer.append(Integer.parseInt(binaryStr.substring(beginIndex, beginIndex+8), 2)).append(".");
			}
			System.out.println("net mask "+i+" ,submask:"+buffer.substring(0,buffer.length()-1));
			
		}
上述代码即可输出1-31掩码位对应的子网掩码列表。其中0xFFFFFFFF << (32 - i)就是得到对应的二进制序列。

ip2long IP地址转换成整型。
long2ip 整型数据转换成IP。
子网掩码转换成掩码长度方式：
$slash_notation = strlen(preg_replace("/0/", "", decbin(ip2long($subnet_mask))));
$bits=strpos(decbin(ip2long($mask)),"0");
子网掩码位长转换成子网掩码形式：
$mask = 0xffffffff << (32 - $mask);
$mask = pow(2,32)-pow(2,(32-$mask));
判断两个地址是否在一个子网内：
function matchCIDR($addr, $cidr) {
list($ip, $mask) = explode('/', $cidr);
return (ip2long($addr) >> (32 - $mask) == ip2long($ip) >> (32 - mask));
}
?>
一个IPv4的类：
//--------------
// IPv4 class
class ipv4
{
var $address;
var $netbits;
//--------------
// Create new class
function ipv4($address,$netbits)
{
$this->address = $address;
$this->netbits = $netbits;
}
//--------------
// Return the IP address
function address() { return ($this->address); }
//--------------
// Return the netbits
function netbits() { return ($this->netbits); }
//--------------
// Return the netmask
function netmask()
{
return (long2ip(ip2long("255.255.255.255")
<< (32-$this->netbits)));
}
//--------------
// Return the network that the address sits in
function network()
{
return (long2ip((ip2long($this->address))
& (ip2long($this->netmask()))));
}
//--------------
// Return the broadcast that the address sits in
function broadcast()
{
return (long2ip(ip2long($this->network())
| (~(ip2long($this->netmask())))));
}
//--------------
// Return the inverse mask of the netmask
function inverse()
{
return (long2ip(~(ip2long("255.255.255.255")
<< (32-$this->netbits))));
}
}
$ip = new ipv4("192.168.2.1",24);
print "Address: $ip->address()\n";
print "Netbits: $ip->netbits()\n";
print "Netmask: $ip->netmask()\n";
print "Inverse: $ip->inverse()\n";
print "Network: $ip->network()\n";
print "Broadcast: $ip->broadcast()\n";
?>
这个做法比较有创意：
For those poor little people using PHP 3, here's an ip2long:
if (!function_exists("ip2long")) {
function ip2long($ip) {
$ex = explode(".", $ip);
if (count($ex)!=4) return -1;
list($a, $b, $c, $d) = $ex;
$a = $a*16777216;
$b = $b*65536;
$c = $c*256;
return $a+$b+$c+$d;
}
}
?>
#!/usr/local/bin/php
$ip_addr = "172.14.1.57";
$subnet_mask = "255.255.255.0";
$ip = ip2long($ip_addr);
$nm = ip2long($subnet_mask);
$nw = ($ip & $nm);
$bc = $nw | (~$nm);
echo "IP Address:         " . long2ip($ip) . "\n";
echo "Subnet Mask:        " . long2ip($nm) . "\n";
echo "Network Address:    " . long2ip($nw) . "\n";
echo "Broadcast Address:  " . long2ip($bc) . "\n";
echo "Number of Hosts:    " . ($bc - $nw - 1) . "\n";
echo "Host Range:         " . long2ip($nw + 1) . " -> " . long2ip($bc - 1)  . "\n";
?>
Produces the output:
IP Address:         172.14.1.57
Subnet Mask:        255.255.255.0
Network Address:    172.14.1.0
Broadcast Address:  172.14.1.255
Number of Hosts:    254
Host Range:         172.14.1.1 -> 172.14.1.254

PHP对IP地址和子网掩码的处理方法(转)
(2011-07-15 11:33:36)
标签：
子网掩码
ipv4
ip地址
数据转换
处理方法
it
分类：
php
ip2long IP地址转换成整型。long2ip 整型数据转换成IP。子网掩码转换成掩码长度方式：$slash_notation =
strlen(preg_replace("/0/", "",
decbin(ip2long($subnet_mask))));$bits=strpos(decbin(ip2long(
...
ip2long IP地址转换成整型。
long2ip 整型数据转换成IP。
子网掩码转换成掩码长度方式：
$slash_notation = strlen(preg_replace("/0/", "",
decbin(ip2long($subnet_mask))));
$bits=strpos(decbin(ip2long($mask)),"0");
子网掩码位长转换成子网掩码形式：
$mask = 0xffffffff << (32 -
$mask);
$mask = pow(2,32)-pow(2,(32-$mask));
判断两个地址是否在一个子网内：
function matchCIDR($addr, $cidr) {
list($ip, $mask) = explode('/', $cidr);
return (ip2long($addr) >> (32 -
$mask) == ip2long($ip) >> (32 -
mask));
}
?>
一个IPv4的类：
//--------------
// IPv4 class
class ipv4
{
var $address;
var $netbits;
//--------------
// Create new class
function ipv4($address,$netbits)
{
$this->address = $address;
$this->netbits = $netbits;
}
//--------------
// Return the IP address
function address() { return ($this->address);
}
//--------------
// Return the netbits
function netbits() { return ($this->netbits);
}
//--------------
// Return the netmask
function netmask()
{
return (long2ip(ip2long("255.255.255.255")
<<
(32-$this->netbits)));
}
//--------------
// Return the network that the address sits in
function network()
{
return (long2ip((ip2long($this->address))
&
(ip2long($this->netmask()))));
}
//--------------
// Return the broadcast that the address sits in
function broadcast()
{
return (long2ip(ip2long($this->network())
| (~(ip2long($this->netmask())))));
}
//--------------
// Return the inverse mask of the netmask
function inverse()
{
return (long2ip(~(ip2long("255.255.255.255")
<<
(32-$this->netbits))));
}
}
$ip = new ipv4("192.168.2.1",24);
print "Address: $ip->address()\n";
print "Netbits: $ip->netbits()\n";
print "Netmask: $ip->netmask()\n";
print "Inverse: $ip->inverse()\n";
print "Network: $ip->network()\n";
print "Broadcast: $ip->broadcast()\n";
?>
这个做法比较有创意：
For those poor little people using PHP 3, here's an ip2long:
if (!function_exists("ip2long")) {
function ip2long($ip) {
$ex = explode(".", $ip);
if (count($ex)!=4) return -1;
list($a, $b, $c, $d) = $ex;
$a = $a*16777216;
$b = $b*65536;
$c = $c*256;
return $a+$b+$c+$d;
}
}
?>
#!/usr/local/bin/php
$ip_addr = "172.14.1.57";
$subnet_mask = "255.255.255.0";
$ip = ip2long($ip_addr);
$nm = ip2long($subnet_mask);
$nw = ($ip & $nm);
$bc = $nw | (~$nm);
echo "IP Address: " . long2ip($ip) . "\n";
echo "Subnet Mask: " . long2ip($nm) . "\n";
echo "Network Address: " . long2ip($nw) . "\n";
echo "Broadcast Address: " . long2ip($bc) . "\n";
echo "Number of Hosts: " . ($bc - $nw - 1) . "\n";
echo "Host Range: " . long2ip($nw + 1) . " -> " .
long2ip($bc - 1) . "\n";
?>
Produces the output:
IP Address: 172.14.1.57
Subnet Mask: 255.255.255.0
Network Address: 172.14.1.0
Broadcast Address: 172.14.1.255
Number of Hosts: 254
Host Range: 172.14.1.1 ->
172.14.1.254
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