Internet Engineering Task Force (IETF) R. Bonica
Request for Comments: 8190 Juniper Networks
BCP: 153 M. Cotton
Updates: 6890 PTI
Category: Best Current Practice B. Haberman
ISSN: 2070-1721 Johns Hopkins University
June 2017 Updates to the Special-Purpose IP Address Registries
This memo updates the IANA IPv4 and IPv6 Special-Purpose Address
Registries to address issues raised by the definition of a "global"
prefix. It also corrects several errors in registry entries to
ensure the integrity of the IANA Special-Purpose Address Registries.
This memo updates RFC 6890.
Status of This Memo
This memo documents an Internet Best Current Practice.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
In order to support new protocols and practices, the IETF
occasionally reserves an address block for a special purpose. For
example, [RFC1122] reserves an IPv4 address block (0.0.0.0/8) to
represent the local (i.e., "this") network. Likewise, [RFC4291]
reserves an IPv6 address block (fe80::/10) for link-local unicast
Several issues have been raised with the documentation of some of the
special-purpose address blocks in [RFC6890]. Specifically, the
definition of "global" provided in [RFC6890] was misleading as it
slightly differed from the generally accepted definition of "global
scope" (i.e., the ability to forward beyond the boundaries of an
administrative domain, described as "global unicast" in the IPv6
addressing architecture [RFC4291]).
This memo updates the definition of "global" from [RFC6890] for the
IPv4 and IPv6 Special-Purpose Address Registries, augments the fields
contained within the registries in order to address the confusion
raised by the definition of "global", and corrects some errors in
some of the entries in the Special-Purpose Address Registries.
This memo updates [RFC6890].
2. IANA Considerations
2.1. Definition of Globally Reachable
[RFC6890] defined the term "global" without taking into consideration
the multiple uses of the term. Specifically, IP addresses can be
global in terms of allocation scope as well as global in terms of
routing/reachability. To address this ambiguity, the use of the term
"global" defined in [RFC6890] is replaced with "globally reachable".
The following definition replaces the definition of "global" in the
IANA Special-Purpose Address Registries:
o Globally Reachable - A boolean value indicating whether an IP
datagram whose destination address is drawn from the allocated
special-purpose address block is forwardable beyond a specified
The same relationship between the value of "Destination" and the
values of "Forwardable" and "Global" described in [RFC6890] holds for
"Globally Reachable". If the value of "Destination" is FALSE, the
values of "Forwardable" and "Globally Reachable" must also be FALSE.
The "Global" columns in the IPv4 Special-Purpose Address Registry
(https://www.iana.org/assignments/iana-ipv4-special-registry) and the
IPv6 Special-Purpose Address Registry
been renamed to "Globally Reachable".
2.2. Updates to the IPv4 Special-Purpose Address Registry
o Limited Broadcast prefix (255.255.255.255/32) - The Reserved-by-
Protocol value has changed from False to True. This change was
made to align the registry with reservation of the limited
broadcast address with Section 7 of [RFC919].
2.3. Updates to the IPv6 Special-Purpose Address Registry
The following changes to the "IPv6 Special-Purpose Address Registry"
involved the insertion of two new footnotes. These additions
required that the footnotes be renumbered.
o TEREDO prefix (2001::/32) - The Globally Reachable value has
changed from False to "N/A ". The  footnote now states:
* See Section 5 of [RFC4380] for details.
o EID Space for LISP (2001:5::/32) - All footnotes have been
incremented by 1.
o 6to4 (2002::/16) - All footnotes have been incremented by 1.
o Unique-Local (fc00::/7) - The Globally Reachable value has changed
from False to "False ". The  footnote now states:
* See [RFC4193] for more details on the routability of Unique-
Local addresses. The Unique-Local prefix is drawn from the
IPv6 Global Unicast Address range but is specified as not
3. Security Considerations
This document does not raise any security issues beyond those
discussed in [RFC6890].
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