SixXS::Sunset 2017-06-06

IPv6 ULA (Unique Local Address) RFC4193 registration

This page allows you to generate and then 'register' your IPv6 ULA (Unique Local Address) RFC4193 prefix. Note that this does not concern ULA-Central, though this system could easily handle that too. When you have registered your ULA prefix here, it allows others to check up if they accidentally generated the same prefix, before using it. This should absolutely minimize the number of collisions for ULA space. We hope that everybody using ULA prefixes register their prefixes here, to avoid these collisions.

See the full list for the currently registered prefixes.

Generate IPv6 Unique Local Address (ULA)

The following form allows one to generate an RFC4193 prefix based of an IEEE MAC address.

Static Edition of the website has ULA generation disabled.

On 2017-06-06 SixXS performed a sunset.

This website is a static edition of the SixXS website.

Please read the Sunsetting SixXS page for more details.

Register IPv6 Unique Local Address (ULA)

Please provide the following details to register your ULA prefix in this registry. We require that these details are provided so that we can properly populate the whois registry. It also used to rate limit bogus registrations. Registering too many prefixes will cause one to be denied access to this interface, this to avoid abuse. The email address is only available either as image or through the whois interface, which is ratelimited, to deter spammers from harvesting them. No email will be sent to this address by SixXS in relation to this registration.

¹ = optional


Warning ULAs were not intended to be registered in any way, it could still be that somebody generates the same prefix and when not checking here, they might use it. As such there is still a chance of collisions. If everybody uses this registry though, the chance for collisions should be near nil. Prefixes which are not generated using the ULA generator will be silently removed; ULAs are not supposed to look pretty.

Prefixes registered here are available from The full list of registered prefixes is available from this file in RPSL inet6num format or the ULA list webpage as mentioned above. The inet6num file does not contain email addresses, this to prevent spammers from collecting them. This file can be cached by other entities, solving any reachability issues, and for archival and redundancy purposes. We hope that one day either IANA/NRO can serve a similar list along with whois and DNS delegations and will provide them full assistance to do so when the time comes.

Updates to entries can be requested by emailing SixXS with the relevant details.


This page uses the Unique Local Address (RFC4193) Generator by SUZUKI Shinsuke and Holger Zuleger. It uses oui.txt from the IEEE OUI Database file.

Static Sunset Edition of SixXS
©2001-2017 SixXS - IPv6 Deployment & Tunnel Broker