IPv6 ULA Generator
Generate RFC 4193-compliant IPv6 Unique Local Addresses from your MAC address with SHA-1. Get a well-spread /48 prefix, first and last host, and EUI-64 details - free and in-browser.
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What is IPv6 ULA Generator?
The IPv6 ULA Generator creates Unique Local Address prefixes (fd00::/8) following the RFC 4193 sample algorithm: EUI-64 from your MAC address is hashed with an NTP timestamp using SHA-1, and the low 40 bits become the Global ID of your /48 prefix.
Key Benefits
- Standards-compliant fd00::/8 prefixes for private networks
- Reproducible generation via optional Unix-millisecond seeds
- Random Global ID mode when no MAC address is handy
- First host, last host, and subnet capacity shown instantly
Common Use Cases
- •Numbering lab, home, or office IPv6 networks
- •Assigning stable internal prefixes across datacenter VLANs
- •Documenting network designs with reproducible ULA blocks
- •Setting up VPN overlays and internal-only services
- •Replacing ad-hoc random prefixes with an RFC-backed process
Generate an IPv6 ULA Prefix
- Enter your MAC address: Type the MAC (EUI-48) address of a machine in your network, e.g. aa:bb:cc:dd:ee:ff. Leave it empty to get a random Global ID instead.
- Optionally fix the timestamp: Enter Unix milliseconds as a seed to make the result reproducible, so the same prefix can be regenerated and documented later.
- Generate the prefix: Click Generate. The tool builds EUI-64, hashes it with an NTP timestamp via SHA-1, and takes the low 40 bits as the Global ID per the RFC 4193 sample algorithm.
- Copy and deploy: Copy the /48 prefix and first/last hosts, then assign /64 subnets within it to your VLANs - up to 65,536 subnets.
Key Features
- RFC 4193 sample algorithm - EUI-64 plus NTP timestamp hashed with SHA-1
- Random Global ID mode when no MAC address is available
- Timestamp seed input for reproducible, documentable prefixes
- First host, last host, and Global ID shown alongside the /48 prefix
- Shows /48 capacity: 2^80 addresses and 65,536 /64 subnets
- One-click copy for prefix and host addresses, fully client-side