IPv6 ULA generator

Generate your own local, non-routable IP addresses for your network according to RFC4193.

Enable JavaScript to use the interactive tool. The guide below explains how it works.

IPv6 ULA Generator: Secure Private Networking for the Modern Internet

In the world of IPv6, Unique Local Addresses (ULAs) serve a similar purpose to private IPv4 addresses (like 192.168.x.x). They allow for local network communication without requiring a globally routable prefix from an ISP. However, unlike IPv4 private ranges, ULAs are designed to be globally unique to avoid address collisions when two private networks are merged.

Using a standardized method to generate these addresses ensures that your internal infrastructure remains consistent and conflict-free, which is vital for enterprise labs, home automation, and container orchestration.

1. What the Tool Does

The IPv6 ULA Generator creates a random /48 IPv6 prefix based on the IETF RFC 4193 specification. It uses a provided MAC address and the current timestamp, processed through a SHA-1 hash, to generate the Global ID. This ensures the resulting address has a very high probability of being globally unique while remaining within the fd00::/8 non-routable range.

2. Why Professionals Use It

• Collision Avoidance: Ensures that if two companies or departments merge their internal networks, their IPv6 addresses won't conflict.
• Stability: Provides a permanent local address for internal services that won't change even if the external ISP-provided prefix does.
• Security: Simplifies internal firewall configurations by using a dedicated local range that is never routed to the public internet.
• Compliance: Follows RFC 4193 standards for generating "locally assigned" Global IDs.

3. Step-by-Step Instructions

1. Provide a MAC address (the tool often provides a default or you can use your own).
2. The tool automatically combines this with the current timestamp.
3. Observe the generated IPv6 ULA prefix (typically starting with fd).
4. Copy the /48 prefix for your router configuration.
5. Use the provided First routable block and Last routable block (/64) to plan your specific subnets.

4. Examples

• Input MAC: 00:1A:2B:3C:4D:5E
  • Output ULA: fdXX:XXXX:XXXX::/48
  • First Subnet: fdXX:XXXX:XXXX:0000::/64
• Scenario: An engineer setting up a Proxmox cluster wants to ensure internal management traffic stays local. They generate a ULA to assign static IPs to their nodes.

5. FAQs

Q: Can I access the internet with a ULA address? A: No, ULA addresses are intentionally non-routable on the public internet. They are for internal network communication only.

Q: Why do I need to provide a MAC address? A: The MAC address acts as a unique seed for the hash function, significantly reducing the chance that another user will generate the same ULA prefix.

6. Common Mistakes

• Using a simple prefix like fd00::1: This violates the randomness requirement of RFC 4193 and leads to collisions. Always use a generated random Global ID.
• Forgetting the "L" bit: ULAs in the fd00::/8 range must have the "L" bit set to 1, which this tool handles automatically.

7. Real-World Use Cases

• Enterprise Intranets: Assigning stable addresses to internal file servers and databases.
• IoT Networks: Providing unique identifiers for hundreds of smart devices without exposing them to the internet.
• Site-to-Site VPNs: Connecting two remote offices without worrying about overlapping private IP ranges.

8. Related Tools

• MAC Address Generator: Generate a random MAC address to use as a seed for this tool.
• IPv4 Subnet Calculator: For managing legacy private network segments.

Future-proof your local network with unique IPv6 identifiers.