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Proposal for IPv6 ULA-central - AFPUB-2007-v6-003

Ref Name AFPUB-2007-v6-003 Old Ref. afpol-v6200607
Status Withdrawn
Date 01 April 2007
Author(s) Jordi Palet Martinez
Organisation Consulintel
  1. Acknowledgments:
  2. Summary of Proposal
  3. Draft Policy Text
  4. Incentive


I would like to acknowledge to the authors of the ULA-central work at IETF, Bob Hinden and Brian Haberman and all those who also contributed to that work.

Summary of Proposal:

This policy is intended to allow the assignment of IPv6 blocks within the so-called ³Centrally Assigned Unique Local IPv6 Unicast Addresses² (see to organizations or individuals requiring it. These addresses are globally unique and intended for local communications, usually within a site or set of them and are not expected to be routable on the global Internet. Prefix FC00::/7 is already reserved by IANA for ULA (bit 8 determines if locally or centrally assigned, so ULA or ULA-central).

Draft Policy Text:

New text, possibly as section 2.6:

2.6. ULA-central
ULA-central refers to the Centrally Assigned Unique Local IPv6 Unicast Addresses as described in the IETF document ³ietf-ipv6-ula-central² (whatever version is the most recent, as an Internet Draft, RFC or STD). The ULA-central block is within the prefix FC00::/7, with bit 8 set to 0.

New text, possibly as section 7:

7. Assignment of ULA-central blocks

Any organization or individual requiring a /48 from the ULA-central block will be able to get it assigned, once the relevant contract is executed and related membership fees are paid (to be determined by the board).

Note that in most of the cases, locally assigned ULA addresses (RFC4193) are preferred, and it is only expected that large managed sites will prefer central assignments. It is also important to reinforce that the ULA prefix
(FC00::/7) it is not routable in the global Internet (i.e., not designed to be used as IPv6 PI) and consequently must be filtered.


a. Arguments Supporting the Proposal

The ³Micro-allocations for Internal Infrastructure² document from ARIN (policy proposal 2006-2, authored by Jason Schiller et al., available at, document describes the need of this kind of additional block for purposes BGP Re-Convergence, Internal Infrastructure Security and why locally assigned ULAs (RFC4193) addresses are not appropriate.

b. Arguments Opposing the Proposal

None foreseen. However, it should be clear that the original scope of ULA-central is for large managed sites and all other cases should use locally assigned ULAs as per RFC4193. From the same document, it is clearly documented the reasons why this prefix will not be useful as IPv6 PI and will be filtered out in the global Internet.

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