Generate RFC 4193 compliant IPv6 Unique Local Addresses (ULA) instantly with our free online tool. Perfect for creating private IPv6 address ranges for internal networks, VPNs, and lab environments.
ULAs are the IPv6 equivalent of private IPv4 addresses (like 192.168.x.x or 10.x.x.x). They are intended for local communications and are not routable on the global Internet.
Format: ULAs use the fd00::/8 prefix. The next 40 bits are the Global ID (randomly generated), followed by a 16-bit Subnet ID, giving you a /48, /56, or /64 prefix for your network.
Use Cases: Internal networks, VPNs, lab environments, and any scenario where you need private IPv6 addressing without risk of conflicts with global addresses.
IPv6 Unique Local Addresses (ULA) are the IPv6 equivalent of private IPv4 addresses like 192.168.x.x or 10.x.x.x. These addresses are designed for local communications within an organization and are not routable on the global Internet.
Private addressing: Not routed on the public Internet
Globally unique: Extremely low probability of address conflicts
RFC 4193 compliant: Follows official Internet standards
Stable addressing: Ideal for internal network infrastructure
Self-generated: No registration or authority needed
Select "Random Generation" method
Choose your preferred prefix length (/48, /56, or /64)
Click the refresh icon to generate a new ULA
Copy the generated address for your network configuration
Select "Custom Global ID" method
Enter a 10-character hexadecimal value (40 bits)
Choose your prefix length
Click "Generate" to create your custom ULA
fd12:3456:789a::/48
fd — ULA prefix (fixed)
12:3456:789a — Global ID (40 bits)
/48 — Prefix length
/48 (Recommended): Provides 65,536 subnets with 264 addresses each
/56: Provides 256 subnets, common for smaller organizations
/64: Single subnet, suitable for specific network segments
ULAs are perfect for internal servers, databases, and services that don't need Internet accessibility. They provide stable addressing that won't conflict with public IPv6 addresses.
Create secure, private address spaces for VPN connections without worrying about address conflicts or public routing concerns.
Ideal for development, testing, and lab environments where you need realistic IPv6 addressing without affecting production networks.
Organize different departments or services with distinct ULA prefixes while maintaining a consistent addressing scheme.
| Feature | ULA (fd00::/8) | Global Unicast |
|---|---|---|
| Routing | Local only | Internet routable |
| Registration | Not required | Required from RIR |
| Cost | Free | May have fees |
| Uniqueness | Statistically unique | Guaranteed unique |
| Use Case | Internal networks | Public services |
Always use cryptographically random generation for the Global ID to ensure uniqueness and avoid conflicts with other organizations, as per RFC 4193 standards.
Keep detailed records of your generated ULA prefixes, including the generation date and intended use case (e.g., staging vs. production) for future reference.
Stick with a /48 prefix length unless you have highly specific requirements. It provides maximum flexibility for network growth and aligns with industry-standard recommendations.
Develop a logical subnetting scheme within your ULA space to keep your infrastructure organized:
fd12:3456:789a:0001::/64 — Data Center
fd12:3456:789a:0002::/64 — Office Network
fd12:3456:789a:0003::/64 — WiFi Guests
Configure firewalls to block ULA traffic at Internet boundaries. This prevents accidental routing "leakage" and ensures your internal traffic stays strictly internal.
Our generator follows RFC 4193 specifications exactly, ensuring compatibility with all IPv6-compliant systems and devices.
Uses the Web Crypto API (crypto.getRandomValues) to generate cryptographically secure random Global IDs, providing excellent uniqueness guarantees.
Prefix: fd00::/8
Global ID: 40 bits (randomly generated)
Subnet ID: 16 bits (user configurable)
Interface ID: 64 bits (assigned by network admin)
Internal file servers
Database servers
Monitoring systems
Management interfaces
Inter-office communications
Smart home devices
Network attached storage (NAS)
Home automation systems
Media servers
Personal cloud services
Customer premise equipment (CPE)
Management VLANs
Backend infrastructure
Testing and staging environments
No. ULAs are designed for local use only and should be filtered at Internet boundaries. ISPs and Internet routers will not forward ULA traffic.
No registration is required. The random generation method provides statistical uniqueness without central coordination.
While technically possible, it's not recommended. Generate unique ULAs for each site to enable future interconnection without address conflicts.
With 40 bits of randomness (over 1 trillion possibilities), the probability of collision is extremely low—approximately 1 in 500 billion for any two organizations.
Use both. ULA for internal-only resources and Global Unicast for Internet-facing services. This provides defense-in-depth security.
Ready to implement IPv6 ULA in your network? Follow these steps:
Generate Your ULA: Use our tool to create a unique /48 prefix
Document the Prefix: Save your ULA prefix in your network documentation
Plan Subnets: Allocate /64 subnets for different network segments
Configure Devices: Implement the ULA addresses on your routers and servers
Update Firewall Rules: Ensure ULA traffic stays within your network
Test Connectivity: Verify internal communication works correctly
Monitor and Maintain: Keep your ULA addressing scheme organized and documented
IPv6 Unique Local Addresses provide a robust solution for private network addressing in the IPv6 era. Our free ULA generator makes it simple to create RFC-compliant addresses for your infrastructure needs.
Whether you're deploying a corporate network, setting up a home lab, or planning a service provider network, proper ULA implementation ensures stable, conflict-free addressing for your internal resources.
Generate your IPv6 ULA prefix now and take the first step toward modern, scalable IPv6 network architecture.