.subnetting-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #fdfdfd;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}
.subnetting-calculator-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
font-size: 1.8em;
}
.subnetting-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-direction: column;
}
.subnetting-calculator-container label {
display: block;
margin-bottom: 8px;
color: #34495e;
font-weight: bold;
font-size: 0.95em;
}
.subnetting-calculator-container input[type="text"],
.subnetting-calculator-container input[type="number"] {
width: calc(100% – 20px);
padding: 12px;
border: 1px solid #ccc;
border-radius: 6px;
font-size: 1em;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.subnetting-calculator-container input[type="text"]:focus,
.subnetting-calculator-container input[type="number"]:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 5px rgba(0, 123, 255, 0.3);
}
.subnetting-calculator-container button {
display: block;
width: 100%;
padding: 14px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 6px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 20px;
}
.subnetting-calculator-container button:hover {
background-color: #0056b3;
transform: translateY(-2px);
}
.subnetting-calculator-container .result-section {
margin-top: 30px;
padding-top: 25px;
border-top: 1px solid #eee;
}
.subnetting-calculator-container .result-section h3 {
color: #2c3e50;
margin-bottom: 15px;
font-size: 1.5em;
text-align: center;
}
.subnetting-calculator-container .result-item {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px dashed #eee;
}
.subnetting-calculator-container .result-item:last-child {
border-bottom: none;
}
.subnetting-calculator-container .result-item strong {
color: #34495e;
flex-basis: 50%;
font-size: 1em;
}
.subnetting-calculator-container .result-item span {
color: #007bff;
flex-basis: 50%;
text-align: right;
font-weight: bold;
font-size: 1em;
}
.subnetting-calculator-container .error-message {
color: #dc3545;
margin-top: 15px;
text-align: center;
font-weight: bold;
}
.subnetting-calculator-container .article-content {
margin-top: 40px;
padding-top: 30px;
border-top: 1px solid #e0e0e0;
line-height: 1.7;
color: #333;
}
.subnetting-calculator-container .article-content h3 {
color: #2c3e50;
margin-top: 25px;
margin-bottom: 15px;
font-size: 1.6em;
}
.subnetting-calculator-container .article-content p {
margin-bottom: 15px;
}
.subnetting-calculator-container .article-content ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 15px;
}
.subnetting-calculator-container .article-content li {
margin-bottom: 8px;
}
function calculateSubnet() {
var ipAddressInput = document.getElementById("ipAddress").value.trim();
var cidrPrefixInput = parseInt(document.getElementById("cidrPrefix").value.trim(), 10);
var errorMessageDiv = document.getElementById("errorMessage");
var subnetResultDiv = document.getElementById("subnetResult");
errorMessageDiv.style.display = "none";
subnetResultDiv.style.display = "none";
// — Input Validation —
var ipParts = ipAddressInput.split('.');
if (ipParts.length !== 4) {
errorMessageDiv.textContent = "Invalid IP Address format. Please use dotted decimal (e.g., 192.168.1.100).";
errorMessageDiv.style.display = "block";
return;
}
var ipOctets = [];
for (var i = 0; i < 4; i++) {
var octet = parseInt(ipParts[i], 10);
if (isNaN(octet) || octet 255) {
errorMessageDiv.textContent = "Invalid IP Address octet. Each part must be between 0 and 255.";
errorMessageDiv.style.display = "block";
return;
}
ipOctets.push(octet);
}
if (isNaN(cidrPrefixInput) || cidrPrefixInput 32) {
errorMessageDiv.textContent = "Invalid CIDR Prefix. Must be a number between 0 and 32.";
errorMessageDiv.style.display = "block";
return;
}
// — Calculations —
// Convert IP to 32-bit integer
var ipInt = (ipOctets[0] << 24) | (ipOctets[1] << 16) | (ipOctets[2] << 8) | ipOctets[3];
// Calculate Subnet Mask (32-bit integer)
var subnetMaskInt = 0xFFFFFFFF <> 24) & 0xFF) + "." +
((intVal >> 16) & 0xFF) + "." +
((intVal >> 8) & 0xFF) + "." +
(intVal & 0xFF);
}
var networkAddress = intToDottedDecimal(networkInt);
var broadcastAddress = intToDottedDecimal(broadcastInt);
var subnetMaskDecimal = intToDottedDecimal(subnetMaskInt);
var wildcardMask = intToDottedDecimal(~subnetMaskInt);
// Calculate First and Last Usable Hosts
var firstHost = "N/A";
var lastHost = "N/A";
var usableHosts = 0;
if (cidrPrefixInput < 31) { // For /31 and /32, there are no usable hosts or only 1
firstHost = intToDottedDecimal(networkInt + 1);
lastHost = intToDottedDecimal(broadcastInt – 1);
usableHosts = Math.pow(2, (32 – cidrPrefixInput)) – 2;
} else if (cidrPrefixInput === 31) { // /31 has 2 addresses, 0 usable hosts
usableHosts = 0;
firstHost = "N/A (Point-to-point link)";
lastHost = "N/A (Point-to-point link)";
} else if (cidrPrefixInput === 32) { // /32 has 1 address, 0 usable hosts
usableHosts = 0;
firstHost = "N/A (Single host address)";
lastHost = "N/A (Single host address)";
}
// — Display Results —
document.getElementById("networkAddress").textContent = networkAddress;
document.getElementById("broadcastAddress").textContent = broadcastAddress;
document.getElementById("firstHost").textContent = firstHost;
document.getElementById("lastHost").textContent = lastHost;
document.getElementById("usableHosts").textContent = usableHosts;
document.getElementById("subnetMaskDecimal").textContent = subnetMaskDecimal;
document.getElementById("cidrOutput").textContent = "/" + cidrPrefixInput;
document.getElementById("wildcardMask").textContent = wildcardMask;
subnetResultDiv.style.display = "block";
}
IP Subnetting Calculator
Subnet Details
Network Address:
Broadcast Address:
First Usable Host:
Last Usable Host:
Number of Usable Hosts:
Subnet Mask (Dotted Decimal):
CIDR Prefix:
Wildcard Mask:
Understanding IP Subnetting
IP subnetting is the process of dividing a larger network into smaller, more manageable subnetworks. This technique is fundamental in network administration for various reasons, including improving network performance, enhancing security, and making more efficient use of IP addresses.
Why Subnet?
- Improved Performance: By reducing the size of broadcast domains, subnetting minimizes unnecessary network traffic, leading to faster communication within each subnet.
- Enhanced Security: Subnetting allows network administrators to isolate different parts of a network, preventing unauthorized access between segments and containing security breaches.
- Efficient IP Address Utilization: Especially with IPv4, subnetting helps conserve IP addresses by allocating only the necessary number of addresses to each subnetwork, rather than assigning a large block to a small group of devices.
- Easier Management: Smaller, logically organized networks are easier to manage, troubleshoot, and scale.
Key Subnetting Concepts
To effectively use this calculator and understand subnetting, it's important to grasp a few core concepts:
- IP Address: A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It consists of four octets (groups of 8 bits) separated by dots, e.g.,
192.168.1.100. - Subnet Mask: A 32-bit number that distinguishes the network portion of an IP address from the host portion. It's also represented in dotted decimal format, e.g.,
255.255.255.0. - CIDR (Classless Inter-Domain Routing) Prefix: A more concise way to represent the subnet mask, indicating the number of bits used for the network portion. For example,
/24is equivalent to255.255.255.0. - Network Address: The first address in a subnet, used to identify the entire network. All host bits are zero.
- Broadcast Address: The last address in a subnet, used to send data to all devices within that subnet. All host bits are one.
- Usable Host Addresses: The range of IP addresses within a subnet that can be assigned to individual devices. This range excludes the network and broadcast addresses.
- Wildcard Mask: The inverse of the subnet mask. It's often used in access control lists (ACLs) to specify a range of IP addresses.
How the Calculator Works
This calculator takes an IP address and a CIDR prefix as input. Based on these values, it performs bitwise operations to determine the various components of the subnet:
- It converts the IP address into its 32-bit binary representation.
- It uses the CIDR prefix to determine the subnet mask in binary. The CIDR prefix indicates how many leading bits are part of the network portion (set to 1 in the subnet mask).
- The Network Address is found by performing a bitwise AND operation between the IP address and the subnet mask.
- The Broadcast Address is found by performing a bitwise OR operation between the Network Address and the inverse of the subnet mask (the wildcard mask).
- The First Usable Host is the Network Address plus one.
- The Last Usable Host is the Broadcast Address minus one.
- The Number of Usable Hosts is calculated as
2^(32 - CIDR Prefix) - 2(subtracting the network and broadcast addresses).
Example Usage
Let's say you have an IP address 192.168.1.100 and a CIDR prefix of /24.
- IP Address:
192.168.1.100 - CIDR Prefix:
24
Upon calculation, the results would be:
- Network Address:
192.168.1.0 - Broadcast Address:
192.168.1.255 - First Usable Host:
192.168.1.1 - Last Usable Host:
192.168.1.254 - Number of Usable Hosts:
254 - Subnet Mask (Dotted Decimal):
255.255.255.0 - CIDR Prefix:
/24 - Wildcard Mask:
0.0.0.255
This calculator simplifies the complex binary math involved in subnetting, making it an invaluable tool for network professionals and students alike.