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Category Network Utilities

Network Configuration

IPv6 Address / Prefix

Accepts compressed (::) or full hex formats.

Calculation Results

Canonical Address (RFC 5952) -

Expanded Address -

Network Prefix -

Start Address -

End Address -

Total /64 Subnets -

Total Host Addresses -

Break down current network into:

Index	Network	Range Start	Range End
Select a target CIDR to view subnets

Generates the PTR record for BIND/Zone files.

ip6.arpa Domain

-

Generates a random Unique Local Address (RFC 4193) using cryptographic entropy.

Resulting Block (fd00::/8)

-

MAC Address

IPv6 Link-Local Address

-

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About

The transition to IPv6 introduces a 128-bit address space, effectively eliminating the address exhaustion issues of IPv4. However, the complexity of hexadecimal notation and the sheer scale of subnets make mental calculation impossible. Precision is non-negotiable; a single bit error in a prefix length can misalign an entire network hierarchy.

This tool is engineered for network architects and systems administrators who require bit-perfect accuracy. It handles the full 128-bit range using BigInt arithmetic, ensuring no loss of precision. Beyond simple range calculation, it provides deep inspection of subnet hierarchies, generates RFC 4193 Unique Local Addresses (ULA), and automates the creation of ip6.arpa reverse DNS records. It addresses the common pitfalls of IPv6 deployment, such as incorrect zero-compression (RFC 5952) and EUI-64 Interface ID generation.

Formulas

IPv6 subnetting relies on bitwise operations over a 128-bit field. The number of hosts in a subnet is defined by the remaining bits after the prefix.

{

Hosts = 2^{128 − P}Subnets = 2^{n − P}

Where P is the parent prefix length and n is the new prefix length.

EUI-64 Generation:
To convert a 48-bit MAC address to a 64-bit Interface ID, 16 bits (0xFFFE) are inserted in the middle, and the Universal/Local (U/L) bit is inverted.

{

MAC = c₁c₂ : c₃c₄ : c₅c₆ : c₇c₈ : c₉c₁₀ : c₁₁c₁₂Insert → ff : feInvert Bit 7 → c₂ ^ 0x02

Reference Data

Prefix	Allocation Type	Description
::/128	Unspecified	The address of all zeros. Used during software initialization.
::1/128	Loopback	Localhost. Equivalent to 127.0.0.1 in IPv4.
2000::/3	Global Unicast	The block for all publicly routable Internet traffic.
fc00::/7	Unique Local (ULA)	Private routing. Analogous to 10.0.0.0/8 in IPv4.
fe80::/10	Link-Local	Auto-configured addresses valid only on a single link.
ff00::/8	Multicast	Used for one-to-many communication.
2001:db8::/32	Documentation	Reserved for use in documentation and examples.
2002::/16	6to4	Transition mechanism prefix.
2001::/32	Teredo	Transition mechanism prefix.

Frequently Asked Questions

The industry standard for a single LAN segment (VLAN) is /64. This is required for SLAAC (Stateless Address Auto-Configuration) to function correctly. Breaking a /64 into smaller subnets (e.g., /96 or /112) breaks auto-configuration and is generally discouraged unless you are manually managing point-to-point links.

ip6.arpa is the domain defined for IPv6 reverse DNS lookups. The address is represented as a sequence of nibbles (4-bit hex characters) in reverse order, separated by dots. This tool automates the tedious process of reversing the 32 nibbles manually.

RFC 5952 defines the canonical text representation of IPv6 addresses to ensure consistency. Rules include: suppressing leading zeros in a group, using lowercase hexadecimal, and shortening the longest sequence of zero groups to "::". This tool automatically formats all outputs to this standard.

ULA addresses (fc00::/7) require a 40-bit Global ID that should be pseudo-random to prevent collisions when networks merge. This tool uses your browser's cryptographic random number generator to create a high-entropy Global ID compliant with RFC 4193.