Networking & Web

IPv6 ULA Generator

Generate a cryptographically random IPv6 Unique Local Address block, ready to assign /64 subnets from for private networks.

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IPv6 ULA Prefix (/48)

Global ID (40 bits)

First Subnet (/64)

IPv6 Unique Local Addresses (ULA)

Unique Local Addresses (ULAs) are IPv6 addresses that are intended for local communication (e.g., within a private enterprise network or home network). They are the IPv6 equivalent of IPv4 private addresses like 10.0.0.0/8 or 192.168.0.0/16.

RFC 4193 Standard

The standard reserves the fc00::/7 block for ULAs. In practice, the L (Local) bit is set to 1, meaning ULAs always start with fd (fd00::/8). The remaining 40 bits form a pseudo-random Global ID, resulting in a /48 prefix.

Why generate randomly?

Unlike IPv4 where everyone uses 192.168.1.0/24, IPv6 ULAs require a 40-bit random global ID. This randomness virtually guarantees that if two different corporate networks merge or connect via VPN, their ULA subnets will not overlap, completely avoiding the IP conflict nightmares common in IPv4 mergers.

Subnetting a /48 ULA

A generated /48 ULA provides 16 bits for subnetting (since a standard IPv6 LAN segment is a /64). This allows for 65,536 subnets (/64s) within your private network, each capable of holding 18 quintillion devices.

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How it works

Three steps, no setup

Generate a global ID

A random 40-bit identifier is created using secure randomness.

Get your ULA prefix

The result follows the standard fd00::/8 private addressing format.

List ready-to-use subnets

See example /64 subnets you can assign directly to VLANs.

Common questions

Frequently asked questions

What is a ULA used for?

Unique Local Addresses are IPv6's equivalent of private IPv4 ranges (like 10.0.0.0/8) — used for addressing inside a network that is not globally routed.

Why is the global ID random?

Randomness keeps the prefix statistically unique even if two private networks are later merged or interconnected.

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Networking & Web

IPv6 ULA Generator

IPv6 Unique Local Addresses (ULA)

RFC 4193 Standard

Why generate randomly?

Subnetting a /48 ULA

Three steps, no setup

Generate a global ID

Get your ULA prefix

List ready-to-use subnets

Frequently asked questions

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IPv6 Unique Local Addresses (ULA)

RFC 4193 Standard

Why generate randomly?

Subnetting a /48 ULA