With the development of the Internet, IP addresses are widely used in various fields. However, the classification of IP addresses has brought certain confusion to network administrators, especially in subnet mask division. A subnet mask is a part of an IP address that determines the network part and host part to which an IP address belongs. In this article, we will share a subnet mask converter implemented in JavaScript to help you better understand the concept and application of subnet masks.

The concept of subnet mask

In IP addresses, subnet masks are used to divide network addresses and host addresses. It consists of 32 bits binary with 1 for the network part and 0 for the host part. The purpose of the subnet mask is to divide an IP address into two parts: the network address and the host address. Taking IPv4 as an example, the subnet mask is usually expressed in terms of "prefix length".

For example, the subnet mask 255.255.255.0 can be written as "/24", where "24" represents the prefix length. This means that the first 24 bits are the network address and the last 8 bits are the host address. In a subnet, a specific IP address can be expressed in the form of "network address host address".

Application of subnet mask

The main function of subnet mask is to divide an IP address into a network address and a host address, thereby realizing network division and management. Usually, all hosts in a network have the same network address, and different host addresses are used to distinguish different hosts. If the subnet mask is set improperly, hosts between subnets will not be able to communicate with each other.

Therefore, in order to ensure normal network communication, the network administrator needs to set the subnet mask correctly. There are three ways to divide subnet masks: Class A, Class B, and Class C. Among them, Class A subnet mask is suitable for large-scale networks, Class B is suitable for medium-sized networks, and Class C is suitable for small-scale networks.

JavaScript to implement a subnet mask converter

Below, we will introduce how to use JavaScript to implement a subnet mask converter. This tool can convert the subnet mask from decimal, binary and Convert between CIDR prefix lengths.

1. HTML code for subnet mask converter

  
  



  
子网掩码转换器
  

    

      子网掩码：
    
    

      
      
      
    
    

      转换结果：
    
  
 
  

This is a simple HTML interface, which contains a text box for entering the subnet mask, three button and a text box showing the conversion results. When the button is clicked, the corresponding JavaScript function will be called for conversion.

2. Convert decimal to binary

function decimalToBinary() {
  var subnetmask = document.getElementById('subnetmask').value.trim();
  var result = '';
  if (subnetmask.length === 0 || isNaN(subnetmask)) {
    result = '请输入正确的十进制数值';
  } else {
    var binary = parseInt(subnetmask).toString(2);
    result = pad(binary, 32);
  }
  document.getElementById('result').value = result;
}

This is a function that converts decimal values ​​into 32-bit binary. It first reads the entered decimal value from the text box and then converts it to binary using the toString() method. Please note that after the conversion is completed, you need to use the pad() function to pad it to 32 bits, which will be helpful for later operations. Finally, display the conversion results in the text box.

3. Convert binary to decimal

function binaryToDecimal() {
  var subnetmask = document.getElementById('subnetmask').value.trim();
  var result = '';
  if (subnetmask.length === 0) {
    result = '请输入正确的二进制数值';
  } else if (!/^[01]{32}$/.test(subnetmask)) {
    result = '请输入32位二进制数值';
  } else {
    var decimal = parseInt(subnetmask, 2).toString();
    result = decimal;
  }
  document.getElementById('result').value = result;
}

This is a function that converts a 32-bit binary value into a decimal value. It first checks whether the input is correct, that is, whether the length is a 32-bit binary value and contains only 0s and 1s. If the input is incorrect, an error message will be returned. Otherwise, use the parseInt() method to convert the binary value to a decimal value and display the result in the text box.

4. Convert CIDR prefix length to subnet mask

function cidrToSubnetmask() {
  var subnetmask = document.getElementById('subnetmask').value.trim();
  var result = '';
  if (subnetmask.length === 0 || isNaN(subnetmask)) {
    result = '请输入正确的CIDR前缀长度';
  } else if (subnetmask < 0 || subnetmask > 32) {
    result = 'CIDR前缀长度必须在0到32之间';
  } else {
    var binary = '1'.repeat(subnetmask) + '0'.repeat(32 - subnetmask);
    var subnetmask = binary.match(/.{1,8}/g).map(function(s) { return parseInt(s, 2); }).join('.');
    result = subnetmask;
  }
  document.getElementById('result').value = result;
}

This is a function that converts CIDR prefix length to subnet mask. It first checks whether the input is correct, i.e. whether the length is a decimal value and within a reasonable range. If the input is incorrect, an error message will be returned. Otherwise, convert the prefix length to a 32-bit binary value and use the match() method to split it into four 8-bit binary values. Then, use the map() method to convert each binary value to a decimal value, and use the join() method to join it into 4 segments. Finally, display the conversion results in the text box.

Summary

In this article, we introduced the concept and application of subnet masks, and shared a subnet mask converter implemented in JavaScript. This tool can help network administrators better understand the concepts and applications of subnet masks, and effectively solve network problems caused by incorrect subnet mask settings. In future network management, we believe that this tool will definitely be helpful to you.

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