IP Subnet Calculator

Calculate subnet information, network addresses, broadcast addresses, and host ranges for IPv4 networks. Perfect for network administrators and IT professionals.

Network Configuration

Input Method:

CIDR Notation IP + Subnet Mask

Network Address (CIDR):

Format: IP_ADDRESS/PREFIX_LENGTH (e.g., 192.168.1.0/24)

Subnet Division (Optional):

Quick Examples:

Subnet Information

Network Summary

Network Address:

192.168.1.0

Broadcast Address:

192.168.1.255

Subnet Mask:

255.255.255.0

CIDR Notation:

192.168.1.0/24

256

Total Addresses

254

Usable Hosts

Prefix Length

Usable Host Range

First Host: 192.168.1.1

Last Host: 192.168.1.254

Binary Representation

Network:

11000000.10101000.00000001.00000000

Subnet Mask:

11111111.11111111.11111111.00000000

Network Classification

IP Class: C

Network Type: Private (RFC 1918)

Wildcard Mask: 0.0.0.255

Reverse DNS: 0.1.168.192.in-addr.arpa

How to Use

Choose your input method: CIDR notation (192.168.1.0/24) or IP address with subnet mask.

Enter the network address or any IP address within the subnet you want to analyze.

Optionally, select how many subnets you want to divide the network into.

Review the subnet information, host ranges, and subnet division results.

Understanding Subnetting

CIDR Notation

Format

IP_ADDRESS/PREFIX_LENGTH

Example: 192.168.1.0/24 means the first 24 bits are the network portion

Common Prefixes

/24 = 255.255.255.0 (256 addresses)

/25 = 255.255.255.128 (128 addresses)

/26 = 255.255.255.192 (64 addresses)

/27 = 255.255.255.224 (32 addresses)

IP Address Classes

Class A

1.0.0.0 - 126.255.255.255

Default: /8 (16.7M hosts)

Class B

128.0.0.0 - 191.255.255.255

Default: /16 (65K hosts)

Class C

192.0.0.0 - 223.255.255.255

Default: /24 (254 hosts)

Private IP Ranges

10.0.0.0/8: 10.0.0.0 - 10.255.255.255 (Class A private)

172.16.0.0/12: 172.16.0.0 - 172.31.255.255 (Class B private)

192.168.0.0/16: 192.168.0.0 - 192.168.255.255 (Class C private)

Applications

Network Administration

• IP address planning
• Network segmentation
• VLAN configuration
• Router configuration
• Firewall rule creation

Security & Isolation

• Network isolation
• DMZ configuration
• Access control lists
• Security zones
• Traffic segmentation

Troubleshooting

• Network connectivity issues
• Routing problems
• IP conflicts
• Subnet verification
• Network documentation

Example Calculations

Example 1: Class C Network

Network: 192.168.1.0/24

Subnet Mask: 255.255.255.0

Network: 192.168.1.0
Broadcast: 192.168.1.255
Host Range: 192.168.1.1 - 192.168.1.254
Total Hosts: 256 (254 usable)

Example 2: Subnet Division

Original: 192.168.1.0/24

Divide into: 4 subnets

Subnet 1: 192.168.1.0/26 (192.168.1.1 - 192.168.1.62)
Subnet 2: 192.168.1.64/26 (192.168.1.65 - 192.168.1.126)
Subnet 3: 192.168.1.128/26 (192.168.1.129 - 192.168.1.190)
Subnet 4: 192.168.1.192/26 (192.168.1.193 - 192.168.1.254)

Example 3: Variable Length Subnet

Network: 10.0.0.0/8

Custom Subnet: 10.1.1.0/25

Network: 10.1.1.0
Broadcast: 10.1.1.127
Host Range: 10.1.1.1 - 10.1.1.126
Total Hosts: 128 (126 usable)

Frequently Asked Questions

What is the difference between network and broadcast addresses?

The network address is the first address in a subnet and identifies the network itself. The broadcast address is the last address and is used to send data to all hosts in the subnet.

Why can't I use the first and last IP addresses for hosts?

The first IP address (network address) identifies the network, and the last IP address (broadcast address) is reserved for broadcasting to all hosts. Only addresses in between can be assigned to individual devices.

How do I choose the right subnet size?

Consider the number of hosts you need now and in the future. Choose a subnet size that provides enough addresses for growth but doesn't waste too many addresses. Common sizes are /24 (254 hosts), /25 (126 hosts), /26 (62 hosts), and /27 (30 hosts).

What is VLSM (Variable Length Subnet Masking)?

VLSM allows you to use different subnet mask lengths within the same network. This enables more efficient use of IP addresses by allocating appropriately sized subnets for different network segments based on their host requirements.