How I generate an IPv6 ULA prefix for a private network

IPv6 ULA prefixes are for private internal networks, similar in spirit to private IPv4 ranges but designed differently.

I use IPv6 ULA Generator for the quick version of this task, then I review the output before relying on it.

The simple idea

IPv6 ULA prefixes are for private internal networks, similar in spirit to private IPv4 ranges but designed differently.

The tool is a shortcut for the mechanical work. It does not remove the need to understand what the result means.

Step 1: Generate a random ULA prefix

Generate a random ULA prefix.

Step 2: Document where it will be used

Document where it will be used.

Step 3: Avoid manually choosing cute or tiny prefixes

Avoid manually choosing cute or tiny prefixes.

Step 4: Use the prefix consistently inside the private network

Use the prefix consistently inside the private network.

Step 5: Do not route ULA addresses on the public internet

Do not route ULA addresses on the public internet.

Step 6: Plan subnets under the prefix

Plan subnets under the prefix.

Step 7: Keep network documentation updated

Keep network documentation updated.

My checklist

Before I trust the result, I check:

• Generate a random ULA prefix.
• Document where it will be used.
• Avoid manually choosing cute or tiny prefixes.
• Use the prefix consistently inside the private network.
• Do not route ULA addresses on the public internet.
• Plan subnets under the prefix.
• Keep network documentation updated.

That review step is what keeps a quick tool from becoming a quick mistake.