Updates to Special-Purpose IP Address Registries

In order to support new protocols and practices, the IETF occasionally reserves an address block for a special purpose. For example, reserves an IPv4 address block (0.0.0.0/8) to represent the local (i.e., "this") network. Likewise, reserves an IPv6 address block (fe80::/10) to represent link-scoped unicast addresses. Several issues have been raised with the documentation of some of the special-purpose address blocks in . Specifically, the definition of "global" provided in 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 ). This memo updates the definition of "global" from 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 .

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 is replaced with "globally reachable". The following definition replaces the definiton of "global" in the IANA Special-Purpose Address Registries: 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 administrative domain. The same relationship between the value of "Destination" and the values of "Forwardable" and "Global" described in holds for "Globally Reachable". If the value of "Destination" is FALSE, the values of "Forwardable" and "Globally Reachable" must also be FALSE. The "Global" column in the IPv4 Special-Purpose Address Registry (https://www.iana.org/assignments/iana-ipv4-special-registry) and the IPv6 Special-Purpose Address Registry (https://www.iana.org/assignments/iana-ipv6-special-registry) is renamed to "Globally Reachable".

Limited Broadcast prefix (255.255.255.255/32) - The Reserved-by-Protocol value is changed from False to True. This change is made to align the registry with reservation of the limited broadcast address with Section 7 of .

The following changes to the IPv6 Special-Purpose Address Registry involves the insertion of two new footnotes. These changes require the footnotes to be re-numbered. TEREDO prefix (2001::/32) - The Globally Reachable value is changed from False to "N/A [2]". The [2] footnote states: See Section 5 of for details. EID Space for LISP (2001:5::/32) - All footnotes are incremented by 1. 6to4 (2002::/16) - All footnotes are incremented by 1. Unique-Local (fc00::/7) - The Globally Reachable value is changed from False to "False [7]". The [7] footnote states: See 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 globally routed.

This document does not raise any security issues beyond those discussed in .

Brian Carpenter and C.M. Heard provided useful comments on initial versions of this document. Daniel Migault provided an in-depth review that helped strengthen the text within the document.