IPv6 CIDR Calculator

Professional IPv6 subnet calculator with advanced features. Calculate network ranges, subnets, and IP addresses with real-time validation and comprehensive results.

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IPv6 CIDR Calculator

Detailed Calculation Results

Input Address Original
The original IPv6 address as entered by the user.
Expanded Address Full Format
The full 128-bit representation without compression.
Network Address Subnet ID
The network portion of the subnet. All host bits are set to zero.
Subnet Mask Binary Mask
The subnet mask in IPv6 format showing network and host portions.
First Usable Address
The first address in the subnet range.
Last Usable Address
The last address in the subnet range.
Total Addresses
Total number of possible addresses in this subnet.
Address Type
Classification of the IPv6 address type.

Network Details

Prefix Length:
Network Bits:
Host Bits:
Subnet Size:
Hexadecimal Notation:
Interface ID Length:

Binary Representation

Network Portion (Red):
Host Portion (Green):
Complete Address:

Advanced Features

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Real-time Validation

Instant validation of IPv6 addresses and CIDR notation with detailed error messages and suggestions.

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Comprehensive Results

Get detailed subnet information including network address, usable range, and total address count.

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Mobile Responsive

Fully optimized for mobile devices with touch-friendly interface and no horizontal scrolling.

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High Performance

Lightning-fast calculations with optimized algorithms and lazy loading for optimal performance.

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Export Results

Copy results to clipboard or download as text file for documentation and sharing.

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Address Analysis

Automatic detection of IPv6 address types including unicast, multicast, and special addresses.

How It Works

1

Enter IPv6 Address

Input your IPv6 address in any valid format. Our validator will check for correctness in real-time.

2

Set Prefix Length

Specify the CIDR prefix length (0-128) to define your subnet size and network boundaries.

3

Calculate & Analyze

Click calculate to get comprehensive subnet information with detailed network analysis.

4

Export Results

Copy results to clipboard or download as a file for documentation and future reference.

Understanding IPv6 and CIDR: A Comprehensive Guide

IPv6 network topology diagram showing hierarchical structure with global routing prefix, subnet ID, and interface identifier segments in modern network infrastructure

What is IPv6?

Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), designed to eventually replace IPv4. With the explosive growth of internet-connected devices, IPv4's 32-bit address space became insufficient. IPv6 uses 128-bit addresses, providing an astronomical number of unique addresses – approximately 340 undecillion (3.4 × 10^38) addresses.

IPv6 Address Structure

IPv6 addresses are represented as eight groups of four hexadecimal digits, separated by colons. For example:

  • Full notation: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
  • Compressed notation: 2001:db8:85a3::8a2e:370:7334
  • With CIDR: 2001:db8::/32
IPv6 address format breakdown showing 128-bit structure divided into network prefix and interface identifier with hexadecimal representation

Understanding CIDR Notation

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and routing Internet Protocol packets. In IPv6, CIDR notation consists of an IPv6 address followed by a slash and a prefix length (0-128).

The prefix length indicates how many bits from the left are used for the network portion:

  • /64: Most common for subnets, provides 2^64 host addresses
  • /48: Typical assignment for organizations
  • /32: Common for ISP allocations
  • /128: Single host address (equivalent to /32 in IPv4)

IPv6 Address Types

IPv6 defines several address types:

  1. Unicast: Identifies a single interface (Global, Link-local, Unique local)
  2. Multicast: Identifies multiple interfaces (starts with ff00::)
  3. Anycast: Identifies multiple interfaces, but packets are delivered to the nearest one
IPv6 subnet calculation workflow diagram showing step-by-step process from input validation to network range determination

How IPv6 CIDR Calculation Works

Calculating IPv6 subnets involves several steps:

  1. Address Validation: Ensure the IPv6 address is properly formatted
  2. Prefix Application: Apply the subnet mask based on the prefix length
  3. Network Identification: Determine the network address by applying the subnet mask
  4. Range Calculation: Calculate the first and last usable addresses
  5. Address Count: Determine the total number of addresses in the subnet

Practical Applications

IPv6 CIDR calculations are essential for:

  • Network planning and design
  • Subnet allocation and management
  • Routing table optimization
  • Security policy implementation
  • Network troubleshooting

Best Practices

When working with IPv6 subnets:

  • Use /64 subnets for end-user networks
  • Plan your addressing scheme hierarchically
  • Reserve space for future growth
  • Document your subnet allocations
  • Use consistent naming conventions

Understanding IPv6 and CIDR is crucial for modern network administration. As IPv4 addresses become scarce, IPv6 adoption continues to grow, making these skills essential for network professionals.

Frequently Asked Questions

IPv4 uses 32-bit addresses with prefix lengths from /8 to /30, while IPv6 uses 128-bit addresses with prefix lengths from /0 to /128. IPv6 provides a much larger address space and simplified addressing structure.

IPv6 addresses can be compressed by removing leading zeros in each group and replacing consecutive groups of zeros with "::". For example, 2001:0db8:0000:0000:0000:0000:0000:0001 becomes 2001:db8::1.

The most common IPv6 subnet size is /64, which provides 2^64 (18.4 quintillion) addresses. This is the recommended subnet size for end-user networks and is required for SLAAC (Stateless Address Autoconfiguration).

Yes, this calculator is perfect for network planning. It provides comprehensive subnet information including network addresses, usable ranges, and total address counts that are essential for network design and documentation.

Our calculator supports all standard IPv6 formats including full notation, compressed notation with "::", and mixed notation. It also handles various CIDR prefix lengths from /0 to /128.

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