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+Network Working Group R. Hinden
+Request for Comments: 3513 Nokia
+Obsoletes: 2373 S. Deering
+Category: Standards Track Cisco Systems
+ April 2003
+
+
+ Internet Protocol Version 6 (IPv6) Addressing Architecture
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ This specification defines the addressing architecture of the IP
+ Version 6 (IPv6) protocol. The document includes the IPv6 addressing
+ model, text representations of IPv6 addresses, definition of IPv6
+ unicast addresses, anycast addresses, and multicast addresses, and an
+ IPv6 node's required addresses.
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+Hinden & Deering Standards Track [Page 1]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+Table of Contents
+
+ 1. Introduction.................................................3
+ 2. IPv6 Addressing..............................................3
+ 2.1 Addressing Model.........................................4
+ 2.2 Text Representation of Addresses.........................4
+ 2.3 Text Representation of Address Prefixes..................5
+ 2.4 Address Type Identification..............................6
+ 2.5 Unicast Addresses........................................7
+ 2.5.1 Interface Identifiers..............................8
+ 2.5.2 The Unspecified Address............................9
+ 2.5.3 The Loopback Address...............................9
+ 2.5.4 Global Unicast Addresses..........................10
+ 2.5.5 IPv6 Addresses with Embedded IPv4 Addresses.......10
+ 2.5.6 Local-use IPv6 Unicast Addresses..................11
+ 2.6 Anycast Addresses.......................................12
+ 2.6.1 Required Anycast Address..........................13
+ 2.7 Multicast Addresses.....................................13
+ 2.7.1 Pre-Defined Multicast Addresses...................15
+ 2.8 A Node's Required Addresses.............................17
+ 3. Security Considerations.....................................17
+ 4. IANA Considerations.........................................18
+ 5. References..................................................19
+ 5.1 Normative References....................................19
+ 5.2 Informative References..................................19
+ APPENDIX A: Creating Modified EUI-64 format Interface IDs......21
+ APPENDIX B: Changes from RFC-2373..............................24
+ Authors' Addresses.............................................25
+ Full Copyright Statement.......................................26
+
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+Hinden & Deering Standards Track [Page 2]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+1. Introduction
+
+ This specification defines the addressing architecture of the IP
+ Version 6 (IPv6) protocol. It includes the basic formats for the
+ various types of IPv6 addresses (unicast, anycast, and multicast).
+
+ The authors would like to acknowledge the contributions of Paul
+ Francis, Scott Bradner, Jim Bound, Brian Carpenter, Matt Crawford,
+ Deborah Estrin, Roger Fajman, Bob Fink, Peter Ford, Bob Gilligan,
+ Dimitry Haskin, Tom Harsch, Christian Huitema, Tony Li, Greg
+ Minshall, Thomas Narten, Erik Nordmark, Yakov Rekhter, Bill Simpson,
+ Sue Thomson, Markku Savela, and Larry Masinter.
+
+2. IPv6 Addressing
+
+ IPv6 addresses are 128-bit identifiers for interfaces and sets of
+ interfaces (where "interface" is as defined in section 2 of [IPV6]).
+ There are three types of addresses:
+
+ Unicast: An identifier for a single interface. A packet sent to a
+ unicast address is delivered to the interface identified
+ by that address.
+
+ Anycast: An identifier for a set of interfaces (typically belonging
+ to different nodes). A packet sent to an anycast address
+ is delivered to one of the interfaces identified by that
+ address (the "nearest" one, according to the routing
+ protocols' measure of distance).
+
+ Multicast: An identifier for a set of interfaces (typically belonging
+ to different nodes). A packet sent to a multicast address
+ is delivered to all interfaces identified by that address.
+
+ There are no broadcast addresses in IPv6, their function being
+ superseded by multicast addresses.
+
+ In this document, fields in addresses are given a specific name, for
+ example "subnet". When this name is used with the term "ID" for
+ identifier after the name (e.g., "subnet ID"), it refers to the
+ contents of the named field. When it is used with the term "prefix"
+ (e.g., "subnet prefix") it refers to all of the address from the left
+ up to and including this field.
+
+ In IPv6, all zeros and all ones are legal values for any field,
+ unless specifically excluded. Specifically, prefixes may contain, or
+ end with, zero-valued fields.
+
+
+
+
+
+Hinden & Deering Standards Track [Page 3]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+2.1 Addressing Model
+
+ IPv6 addresses of all types are assigned to interfaces, not nodes.
+ An IPv6 unicast address refers to a single interface. Since each
+ interface belongs to a single node, any of that node's interfaces'
+ unicast addresses may be used as an identifier for the node.
+
+ All interfaces are required to have at least one link-local unicast
+ address (see section 2.8 for additional required addresses). A
+ single interface may also have multiple IPv6 addresses of any type
+ (unicast, anycast, and multicast) or scope. Unicast addresses with
+ scope greater than link-scope are not needed for interfaces that are
+ not used as the origin or destination of any IPv6 packets to or from
+ non-neighbors. This is sometimes convenient for point-to-point
+ interfaces. There is one exception to this addressing model:
+
+ A unicast address or a set of unicast addresses may be assigned to
+ multiple physical interfaces if the implementation treats the
+ multiple physical interfaces as one interface when presenting it
+ to the internet layer. This is useful for load-sharing over
+ multiple physical interfaces.
+
+ Currently IPv6 continues the IPv4 model that a subnet prefix is
+ associated with one link. Multiple subnet prefixes may be assigned
+ to the same link.
+
+2.2 Text Representation of Addresses
+
+ There are three conventional forms for representing IPv6 addresses as
+ text strings:
+
+ 1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the
+ hexadecimal values of the eight 16-bit pieces of the address.
+
+ Examples:
+
+ FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
+
+ 1080:0:0:0:8:800:200C:417A
+
+ Note that it is not necessary to write the leading zeros in an
+ individual field, but there must be at least one numeral in every
+ field (except for the case described in 2.).
+
+ 2. Due to some methods of allocating certain styles of IPv6
+ addresses, it will be common for addresses to contain long strings
+ of zero bits. In order to make writing addresses containing zero
+ bits easier a special syntax is available to compress the zeros.
+
+
+
+Hinden & Deering Standards Track [Page 4]
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
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+ The use of "::" indicates one or more groups of 16 bits of zeros.
+ The "::" can only appear once in an address. The "::" can also be
+ used to compress leading or trailing zeros in an address.
+
+ For example, the following addresses:
+
+ 1080:0:0:0:8:800:200C:417A a unicast address
+ FF01:0:0:0:0:0:0:101 a multicast address
+ 0:0:0:0:0:0:0:1 the loopback address
+ 0:0:0:0:0:0:0:0 the unspecified addresses
+
+ may be represented as:
+
+ 1080::8:800:200C:417A a unicast address
+ FF01::101 a multicast address
+ ::1 the loopback address
+ :: the unspecified addresses
+
+ 3. An alternative form that is sometimes more convenient when dealing
+ with a mixed environment of IPv4 and IPv6 nodes is
+ x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of
+ the six high-order 16-bit pieces of the address, and the 'd's are
+ the decimal values of the four low-order 8-bit pieces of the
+ address (standard IPv4 representation). Examples:
+
+ 0:0:0:0:0:0:13.1.68.3
+
+ 0:0:0:0:0:FFFF:129.144.52.38
+
+ or in compressed form:
+
+ ::13.1.68.3
+
+ ::FFFF:129.144.52.38
+
+2.3 Text Representation of Address Prefixes
+
+ The text representation of IPv6 address prefixes is similar to the
+ way IPv4 addresses prefixes are written in CIDR notation [CIDR]. An
+ IPv6 address prefix is represented by the notation:
+
+ ipv6-address/prefix-length
+
+ where
+
+ ipv6-address is an IPv6 address in any of the notations listed
+ in section 2.2.
+
+
+
+
+Hinden & Deering Standards Track [Page 5]
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ prefix-length is a decimal value specifying how many of the
+ leftmost contiguous bits of the address comprise
+ the prefix.
+
+ For example, the following are legal representations of the 60-bit
+ prefix 12AB00000000CD3 (hexadecimal):
+
+ 12AB:0000:0000:CD30:0000:0000:0000:0000/60
+ 12AB::CD30:0:0:0:0/60
+ 12AB:0:0:CD30::/60
+
+ The following are NOT legal representations of the above prefix:
+
+ 12AB:0:0:CD3/60 may drop leading zeros, but not trailing zeros,
+ within any 16-bit chunk of the address
+
+ 12AB::CD30/60 address to left of "/" expands to
+ 12AB:0000:0000:0000:0000:000:0000:CD30
+
+ 12AB::CD3/60 address to left of "/" expands to
+ 12AB:0000:0000:0000:0000:000:0000:0CD3
+
+ When writing both a node address and a prefix of that node address
+ (e.g., the node's subnet prefix), the two can combined as follows:
+
+ the node address 12AB:0:0:CD30:123:4567:89AB:CDEF
+ and its subnet number 12AB:0:0:CD30::/60
+
+ can be abbreviated as 12AB:0:0:CD30:123:4567:89AB:CDEF/60
+
+2.4 Address Type Identification
+
+ The type of an IPv6 address is identified by the high-order bits of
+ the address, as follows:
+
+ Address type Binary prefix IPv6 notation Section
+ ------------ ------------- ------------- -------
+ Unspecified 00...0 (128 bits) ::/128 2.5.2
+ Loopback 00...1 (128 bits) ::1/128 2.5.3
+ Multicast 11111111 FF00::/8 2.7
+ Link-local unicast 1111111010 FE80::/10 2.5.6
+ Site-local unicast 1111111011 FEC0::/10 2.5.6
+ Global unicast (everything else)
+
+ Anycast addresses are taken from the unicast address spaces (of any
+ scope) and are not syntactically distinguishable from unicast
+ addresses.
+
+
+
+
+Hinden & Deering Standards Track [Page 6]
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ The general format of global unicast addresses is described in
+ section 2.5.4. Some special-purpose subtypes of global unicast
+ addresses which contain embedded IPv4 addresses (for the purposes of
+ IPv4-IPv6 interoperation) are described in section 2.5.5.
+
+ Future specifications may redefine one or more sub-ranges of the
+ global unicast space for other purposes, but unless and until that
+ happens, implementations must treat all addresses that do not start
+ with any of the above-listed prefixes as global unicast addresses.
+
+2.5 Unicast Addresses
+
+ IPv6 unicast addresses are aggregable with prefixes of arbitrary
+ bit-length similar to IPv4 addresses under Classless Interdomain
+ Routing.
+
+ There are several types of unicast addresses in IPv6, in particular
+ global unicast, site-local unicast, and link-local unicast. There
+ are also some special-purpose subtypes of global unicast, such as
+ IPv6 addresses with embedded IPv4 addresses or encoded NSAP
+ addresses. Additional address types or subtypes can be defined in
+ the future.
+
+ IPv6 nodes may have considerable or little knowledge of the internal
+ structure of the IPv6 address, depending on the role the node plays
+ (for instance, host versus router). At a minimum, a node may
+ consider that unicast addresses (including its own) have no internal
+ structure:
+
+ | 128 bits |
+ +-----------------------------------------------------------------+
+ | node address |
+ +-----------------------------------------------------------------+
+
+ A slightly sophisticated host (but still rather simple) may
+ additionally be aware of subnet prefix(es) for the link(s) it is
+ attached to, where different addresses may have different values for
+ n:
+
+ | n bits | 128-n bits |
+ +------------------------------------------------+----------------+
+ | subnet prefix | interface ID |
+ +------------------------------------------------+----------------+
+
+ Though a very simple router may have no knowledge of the internal
+ structure of IPv6 unicast addresses, routers will more generally have
+ knowledge of one or more of the hierarchical boundaries for the
+ operation of routing protocols. The known boundaries will differ
+
+
+
+Hinden & Deering Standards Track [Page 7]
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
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+ from router to router, depending on what positions the router holds
+ in the routing hierarchy.
+
+2.5.1 Interface Identifiers
+
+ Interface identifiers in IPv6 unicast addresses are used to identify
+ interfaces on a link. They are required to be unique within a subnet
+ prefix. It is recommended that the same interface identifier not be
+ assigned to different nodes on a link. They may also be unique over
+ a broader scope. In some cases an interface's identifier will be
+ derived directly from that interface's link-layer address. The same
+ interface identifier may be used on multiple interfaces on a single
+ node, as long as they are attached to different subnets.
+
+ Note that the uniqueness of interface identifiers is independent of
+ the uniqueness of IPv6 addresses. For example, a global unicast
+ address may be created with a non-global scope interface identifier
+ and a site-local address may be created with a global scope interface
+ identifier.
+
+ For all unicast addresses, except those that start with binary value
+ 000, Interface IDs are required to be 64 bits long and to be
+ constructed in Modified EUI-64 format.
+
+ Modified EUI-64 format based Interface identifiers may have global
+ scope when derived from a global token (e.g., IEEE 802 48-bit MAC or
+ IEEE EUI-64 identifiers [EUI64]) or may have local scope where a
+ global token is not available (e.g., serial links, tunnel end-points,
+ etc.) or where global tokens are undesirable (e.g., temporary tokens
+ for privacy [PRIV]).
+
+ Modified EUI-64 format interface identifiers are formed by inverting
+ the "u" bit (universal/local bit in IEEE EUI-64 terminology) when
+ forming the interface identifier from IEEE EUI-64 identifiers. In
+ the resulting Modified EUI-64 format the "u" bit is set to one (1) to
+ indicate global scope, and it is set to zero (0) to indicate local
+ scope. The first three octets in binary of an IEEE EUI-64 identifier
+ are as follows:
+
+ 0 0 0 1 1 2
+ |0 7 8 5 6 3|
+ +----+----+----+----+----+----+
+ |cccc|ccug|cccc|cccc|cccc|cccc|
+ +----+----+----+----+----+----+
+
+ written in Internet standard bit-order , where "u" is the
+ universal/local bit, "g" is the individual/group bit, and "c" are the
+ bits of the company_id. Appendix A: "Creating Modified EUI-64 format
+
+
+
+Hinden & Deering Standards Track [Page 8]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ Interface Identifiers" provides examples on the creation of Modified
+ EUI-64 format based interface identifiers.
+
+ The motivation for inverting the "u" bit when forming an interface
+ identifier is to make it easy for system administrators to hand
+ configure non-global identifiers when hardware tokens are not
+ available. This is expected to be case for serial links, tunnel end-
+ points, etc. The alternative would have been for these to be of the
+ form 0200:0:0:1, 0200:0:0:2, etc., instead of the much simpler 1, 2,
+ etc.
+
+ The use of the universal/local bit in the Modified EUI-64 format
+ identifier is to allow development of future technology that can take
+ advantage of interface identifiers with global scope.
+
+ The details of forming interface identifiers are defined in the
+ appropriate "IPv6 over <link>" specification such as "IPv6 over
+ Ethernet" [ETHER], "IPv6 over FDDI" [FDDI], etc.
+
+2.5.2 The Unspecified Address
+
+ The address 0:0:0:0:0:0:0:0 is called the unspecified address. It
+ must never be assigned to any node. It indicates the absence of an
+ address. One example of its use is in the Source Address field of
+ any IPv6 packets sent by an initializing host before it has learned
+ its own address.
+
+ The unspecified address must not be used as the destination address
+ of IPv6 packets or in IPv6 Routing Headers. An IPv6 packet with a
+ source address of unspecified must never be forwarded by an IPv6
+ router.
+
+2.5.3 The Loopback Address
+
+ The unicast address 0:0:0:0:0:0:0:1 is called the loopback address.
+ It may be used by a node to send an IPv6 packet to itself. It may
+ never be assigned to any physical interface. It is treated as
+ having link-local scope, and may be thought of as the link-local
+ unicast address of a virtual interface (typically called "the
+ loopback interface") to an imaginary link that goes nowhere.
+
+ The loopback address must not be used as the source address in IPv6
+ packets that are sent outside of a single node. An IPv6 packet with
+ a destination address of loopback must never be sent outside of a
+ single node and must never be forwarded by an IPv6 router. A packet
+ received on an interface with destination address of loopback must be
+ dropped.
+
+
+
+
+Hinden & Deering Standards Track [Page 9]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+2.5.4 Global Unicast Addresses
+
+ The general format for IPv6 global unicast addresses is as follows:
+
+ | n bits | m bits | 128-n-m bits |
+ +------------------------+-----------+----------------------------+
+ | global routing prefix | subnet ID | interface ID |
+ +------------------------+-----------+----------------------------+
+
+ where the global routing prefix is a (typically hierarchically-
+ structured) value assigned to a site (a cluster of subnets/links),
+ the subnet ID is an identifier of a link within the site, and the
+ interface ID is as defined in section 2.5.1.
+
+ All global unicast addresses other than those that start with binary
+ 000 have a 64-bit interface ID field (i.e., n + m = 64), formatted as
+ described in section 2.5.1. Global unicast addresses that start with
+ binary 000 have no such constraint on the size or structure of the
+ interface ID field.
+
+ Examples of global unicast addresses that start with binary 000 are
+ the IPv6 address with embedded IPv4 addresses described in section
+ 2.5.5 and the IPv6 address containing encoded NSAP addresses
+ specified in [NSAP]. An example of global addresses starting with a
+ binary value other than 000 (and therefore having a 64-bit interface
+ ID field) can be found in [AGGR].
+
+2.5.5 IPv6 Addresses with Embedded IPv4 Addresses
+
+ The IPv6 transition mechanisms [TRAN] include a technique for hosts
+ and routers to dynamically tunnel IPv6 packets over IPv4 routing
+ infrastructure. IPv6 nodes that use this technique are assigned
+ special IPv6 unicast addresses that carry a global IPv4 address in
+ the low-order 32 bits. This type of address is termed an "IPv4-
+ compatible IPv6 address" and has the format:
+
+ | 80 bits | 16 | 32 bits |
+ +--------------------------------------+--------------------------+
+ |0000..............................0000|0000| IPv4 address |
+ +--------------------------------------+----+---------------------+
+
+ Note: The IPv4 address used in the "IPv4-compatible IPv6 address"
+ must be a globally-unique IPv4 unicast address.
+
+ A second type of IPv6 address which holds an embedded IPv4 address is
+ also defined. This address type is used to represent the addresses
+ of IPv4 nodes as IPv6 addresses. This type of address is termed an
+ "IPv4-mapped IPv6 address" and has the format:
+
+
+
+Hinden & Deering Standards Track [Page 10]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ | 80 bits | 16 | 32 bits |
+ +--------------------------------------+--------------------------+
+ |0000..............................0000|FFFF| IPv4 address |
+ +--------------------------------------+----+---------------------+
+
+2.5.6 Local-Use IPv6 Unicast Addresses
+
+ There are two types of local-use unicast addresses defined. These
+ are Link-Local and Site-Local. The Link-Local is for use on a single
+ link and the Site-Local is for use in a single site. Link-Local
+ addresses have the following format:
+
+ | 10 |
+ | bits | 54 bits | 64 bits |
+ +----------+-------------------------+----------------------------+
+ |1111111010| 0 | interface ID |
+ +----------+-------------------------+----------------------------+
+
+ Link-Local addresses are designed to be used for addressing on a
+ single link for purposes such as automatic address configuration,
+ neighbor discovery, or when no routers are present.
+
+ Routers must not forward any packets with link-local source or
+ destination addresses to other links.
+
+ Site-Local addresses have the following format:
+
+ | 10 |
+ | bits | 54 bits | 64 bits |
+ +----------+-------------------------+----------------------------+
+ |1111111011| subnet ID | interface ID |
+ +----------+-------------------------+----------------------------+
+
+ Site-local addresses are designed to be used for addressing inside of
+ a site without the need for a global prefix. Although a subnet ID
+ may be up to 54-bits long, it is expected that globally-connected
+ sites will use the same subnet IDs for site-local and global
+ prefixes.
+
+ Routers must not forward any packets with site-local source or
+ destination addresses outside of the site.
+
+
+
+
+
+
+
+
+
+
+Hinden & Deering Standards Track [Page 11]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+2.6 Anycast Addresses
+
+ An IPv6 anycast address is an address that is assigned to more than
+ one interface (typically belonging to different nodes), with the
+ property that a packet sent to an anycast address is routed to the
+ "nearest" interface having that address, according to the routing
+ protocols' measure of distance.
+
+ Anycast addresses are allocated from the unicast address space, using
+ any of the defined unicast address formats. Thus, anycast addresses
+ are syntactically indistinguishable from unicast addresses. When a
+ unicast address is assigned to more than one interface, thus turning
+ it into an anycast address, the nodes to which the address is
+ assigned must be explicitly configured to know that it is an anycast
+ address.
+
+ For any assigned anycast address, there is a longest prefix P of that
+ address that identifies the topological region in which all
+ interfaces belonging to that anycast address reside. Within the
+ region identified by P, the anycast address must be maintained as a
+ separate entry in the routing system (commonly referred to as a "host
+ route"); outside the region identified by P, the anycast address may
+ be aggregated into the routing entry for prefix P.
+
+ Note that in the worst case, the prefix P of an anycast set may be
+ the null prefix, i.e., the members of the set may have no topological
+ locality. In that case, the anycast address must be maintained as a
+ separate routing entry throughout the entire internet, which presents
+ a severe scaling limit on how many such "global" anycast sets may be
+ supported. Therefore, it is expected that support for global anycast
+ sets may be unavailable or very restricted.
+
+ One expected use of anycast addresses is to identify the set of
+ routers belonging to an organization providing internet service.
+ Such addresses could be used as intermediate addresses in an IPv6
+ Routing header, to cause a packet to be delivered via a particular
+ service provider or sequence of service providers.
+
+ Some other possible uses are to identify the set of routers attached
+ to a particular subnet, or the set of routers providing entry into a
+ particular routing domain.
+
+ There is little experience with widespread, arbitrary use of internet
+ anycast addresses, and some known complications and hazards when
+ using them in their full generality [ANYCST]. Until more experience
+ has been gained and solutions are specified, the following
+ restrictions are imposed on IPv6 anycast addresses:
+
+
+
+
+Hinden & Deering Standards Track [Page 12]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ o An anycast address must not be used as the source address of an
+ IPv6 packet.
+
+ o An anycast address must not be assigned to an IPv6 host, that is,
+ it may be assigned to an IPv6 router only.
+
+2.6.1 Required Anycast Address
+
+ The Subnet-Router anycast address is predefined. Its format is as
+ follows:
+
+ | n bits | 128-n bits |
+ +------------------------------------------------+----------------+
+ | subnet prefix | 00000000000000 |
+ +------------------------------------------------+----------------+
+
+ The "subnet prefix" in an anycast address is the prefix which
+ identifies a specific link. This anycast address is syntactically
+ the same as a unicast address for an interface on the link with the
+ interface identifier set to zero.
+
+ Packets sent to the Subnet-Router anycast address will be delivered
+ to one router on the subnet. All routers are required to support the
+ Subnet-Router anycast addresses for the subnets to which they have
+ interfaces.
+
+ The subnet-router anycast address is intended to be used for
+ applications where a node needs to communicate with any one of the
+ set of routers.
+
+2.7 Multicast Addresses
+
+ An IPv6 multicast address is an identifier for a group of interfaces
+ (typically on different nodes). An interface may belong to any
+ number of multicast groups. Multicast addresses have the following
+ format:
+
+ | 8 | 4 | 4 | 112 bits |
+ +------ -+----+----+---------------------------------------------+
+ |11111111|flgs|scop| group ID |
+ +--------+----+----+---------------------------------------------+
+
+ binary 11111111 at the start of the address identifies the
+ address as being a multicast address.
+
+ +-+-+-+-+
+ flgs is a set of 4 flags: |0|0|0|T|
+ +-+-+-+-+
+
+
+
+Hinden & Deering Standards Track [Page 13]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ The high-order 3 flags are reserved, and must be initialized
+ to 0.
+
+ T = 0 indicates a permanently-assigned ("well-known")
+ multicast address, assigned by the Internet Assigned Number
+ Authority (IANA).
+
+ T = 1 indicates a non-permanently-assigned ("transient")
+ multicast address.
+
+ scop is a 4-bit multicast scope value used to limit the scope
+ of the multicast group. The values are:
+
+ 0 reserved
+ 1 interface-local scope
+ 2 link-local scope
+ 3 reserved
+ 4 admin-local scope
+ 5 site-local scope
+ 6 (unassigned)
+ 7 (unassigned)
+ 8 organization-local scope
+ 9 (unassigned)
+ A (unassigned)
+ B (unassigned)
+ C (unassigned)
+ D (unassigned)
+ E global scope
+ F reserved
+
+ interface-local scope spans only a single interface on a
+ node, and is useful only for loopback transmission of
+ multicast.
+
+ link-local and site-local multicast scopes span the same
+ topological regions as the corresponding unicast scopes.
+
+ admin-local scope is the smallest scope that must be
+ administratively configured, i.e., not automatically derived
+ from physical connectivity or other, non- multicast-related
+ configuration.
+
+ organization-local scope is intended to span multiple sites
+ belonging to a single organization.
+
+ scopes labeled "(unassigned)" are available for
+ administrators to define additional multicast regions.
+
+
+
+
+Hinden & Deering Standards Track [Page 14]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ group ID identifies the multicast group, either permanent or
+ transient, within the given scope.
+
+ The "meaning" of a permanently-assigned multicast address is
+ independent of the scope value. For example, if the "NTP servers
+ group" is assigned a permanent multicast address with a group ID of
+ 101 (hex), then:
+
+ FF01:0:0:0:0:0:0:101 means all NTP servers on the same interface
+ (i.e., the same node) as the sender.
+
+ FF02:0:0:0:0:0:0:101 means all NTP servers on the same link as the
+ sender.
+
+ FF05:0:0:0:0:0:0:101 means all NTP servers in the same site as the
+ sender.
+
+ FF0E:0:0:0:0:0:0:101 means all NTP servers in the internet.
+
+ Non-permanently-assigned multicast addresses are meaningful only
+ within a given scope. For example, a group identified by the non-
+ permanent, site-local multicast address FF15:0:0:0:0:0:0:101 at one
+ site bears no relationship to a group using the same address at a
+ different site, nor to a non-permanent group using the same group ID
+ with different scope, nor to a permanent group with the same group
+ ID.
+
+ Multicast addresses must not be used as source addresses in IPv6
+ packets or appear in any Routing header.
+
+ Routers must not forward any multicast packets beyond of the scope
+ indicated by the scop field in the destination multicast address.
+
+ Nodes must not originate a packet to a multicast address whose scop
+ field contains the reserved value 0; if such a packet is received, it
+ must be silently dropped. Nodes should not originate a packet to a
+ multicast address whose scop field contains the reserved value F; if
+ such a packet is sent or received, it must be treated the same as
+ packets destined to a global (scop E) multicast address.
+
+2.7.1 Pre-Defined Multicast Addresses
+
+ The following well-known multicast addresses are pre-defined. The
+ group ID's defined in this section are defined for explicit scope
+ values.
+
+ Use of these group IDs for any other scope values, with the T flag
+ equal to 0, is not allowed.
+
+
+
+Hinden & Deering Standards Track [Page 15]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ Reserved Multicast Addresses: FF00:0:0:0:0:0:0:0
+ FF01:0:0:0:0:0:0:0
+ FF02:0:0:0:0:0:0:0
+ FF03:0:0:0:0:0:0:0
+ FF04:0:0:0:0:0:0:0
+ FF05:0:0:0:0:0:0:0
+ FF06:0:0:0:0:0:0:0
+ FF07:0:0:0:0:0:0:0
+ FF08:0:0:0:0:0:0:0
+ FF09:0:0:0:0:0:0:0
+ FF0A:0:0:0:0:0:0:0
+ FF0B:0:0:0:0:0:0:0
+ FF0C:0:0:0:0:0:0:0
+ FF0D:0:0:0:0:0:0:0
+ FF0E:0:0:0:0:0:0:0
+ FF0F:0:0:0:0:0:0:0
+
+ The above multicast addresses are reserved and shall never be
+ assigned to any multicast group.
+
+ All Nodes Addresses: FF01:0:0:0:0:0:0:1
+ FF02:0:0:0:0:0:0:1
+
+ The above multicast addresses identify the group of all IPv6 nodes,
+ within scope 1 (interface-local) or 2 (link-local).
+
+ All Routers Addresses: FF01:0:0:0:0:0:0:2
+ FF02:0:0:0:0:0:0:2
+ FF05:0:0:0:0:0:0:2
+
+ The above multicast addresses identify the group of all IPv6 routers,
+ within scope 1 (interface-local), 2 (link-local), or 5 (site-local).
+
+ Solicited-Node Address: FF02:0:0:0:0:1:FFXX:XXXX
+
+ Solicited-node multicast address are computed as a function of a
+ node's unicast and anycast addresses. A solicited-node multicast
+ address is formed by taking the low-order 24 bits of an address
+ (unicast or anycast) and appending those bits to the prefix
+ FF02:0:0:0:0:1:FF00::/104 resulting in a multicast address in the
+ range
+
+ FF02:0:0:0:0:1:FF00:0000
+
+ to
+
+ FF02:0:0:0:0:1:FFFF:FFFF
+
+
+
+
+Hinden & Deering Standards Track [Page 16]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ For example, the solicited node multicast address corresponding to
+ the IPv6 address 4037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. IPv6
+ addresses that differ only in the high-order bits, e.g., due to
+ multiple high-order prefixes associated with different aggregations,
+ will map to the same solicited-node address thereby, reducing the
+ number of multicast addresses a node must join.
+
+ A node is required to compute and join (on the appropriate interface)
+ the associated Solicited-Node multicast addresses for every unicast
+ and anycast address it is assigned.
+
+2.8 A Node's Required Addresses
+
+ A host is required to recognize the following addresses as
+ identifying itself:
+
+ o Its required Link-Local Address for each interface.
+ o Any additional Unicast and Anycast Addresses that have been
+ configured for the node's interfaces (manually or
+ automatically).
+ o The loopback address.
+ o The All-Nodes Multicast Addresses defined in section 2.7.1.
+ o The Solicited-Node Multicast Address for each of its unicast
+ and anycast addresses.
+ o Multicast Addresses of all other groups to which the node
+ belongs.
+
+ A router is required to recognize all addresses that a host is
+ required to recognize, plus the following addresses as identifying
+ itself:
+
+ o The Subnet-Router Anycast Addresses for all interfaces for
+ which it is configured to act as a router.
+ o All other Anycast Addresses with which the router has been
+ configured.
+ o The All-Routers Multicast Addresses defined in section 2.7.1.
+
+3. Security Considerations
+
+ IPv6 addressing documents do not have any direct impact on Internet
+ infrastructure security. Authentication of IPv6 packets is defined
+ in [AUTH].
+
+
+
+
+
+
+
+
+
+Hinden & Deering Standards Track [Page 17]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+4. IANA Considerations
+
+ The table and notes at http://www.isi.edu/in-
+ notes/iana/assignments/ipv6-address-space.txt should be replaced with
+ the following:
+
+ INTERNET PROTOCOL VERSION 6 ADDRESS SPACE
+
+ The initial assignment of IPv6 address space is as follows:
+
+ Allocation Prefix Fraction of
+ (binary) Address Space
+ ----------------------------------- -------- -------------
+ Unassigned (see Note 1 below) 0000 0000 1/256
+ Unassigned 0000 0001 1/256
+ Reserved for NSAP Allocation 0000 001 1/128 [RFC1888]
+ Unassigned 0000 01 1/64
+ Unassigned 0000 1 1/32
+ Unassigned 0001 1/16
+ Global Unicast 001 1/8 [RFC2374]
+ Unassigned 010 1/8
+ Unassigned 011 1/8
+ Unassigned 100 1/8
+ Unassigned 101 1/8
+ Unassigned 110 1/8
+ Unassigned 1110 1/16
+ Unassigned 1111 0 1/32
+ Unassigned 1111 10 1/64
+ Unassigned 1111 110 1/128
+ Unassigned 1111 1110 0 1/512
+ Link-Local Unicast Addresses 1111 1110 10 1/1024
+ Site-Local Unicast Addresses 1111 1110 11 1/1024
+ Multicast Addresses 1111 1111 1/256
+
+ Notes:
+
+ 1. The "unspecified address", the "loopback address", and the IPv6
+ Addresses with Embedded IPv4 Addresses are assigned out of the
+ 0000 0000 binary prefix space.
+
+ 2. For now, IANA should limit its allocation of IPv6 unicast address
+ space to the range of addresses that start with binary value 001.
+ The rest of the global unicast address space (approximately 85% of
+ the IPv6 address space) is reserved for future definition and use,
+ and is not to be assigned by IANA at this time.
+
+
+
+
+
+
+Hinden & Deering Standards Track [Page 18]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+5. References
+
+5.1 Normative References
+
+ [IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
+ (IPv6) Specification", RFC 2460, December 1998.
+
+ [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
+ 3", BCP 9 , RFC 2026, October 1996.
+
+5.2 Informative References
+
+ [ANYCST] Partridge, C., Mendez, T. and W. Milliken, "Host Anycasting
+ Service", RFC 1546, November 1993.
+
+ [AUTH] Kent, S. and R. Atkinson, "IP Authentication Header", RFC
+ 2402, November 1998.
+
+ [AGGR] Hinden, R., O'Dell, M. and S. Deering, "An Aggregatable
+ Global Unicast Address Format", RFC 2374, July 1998.
+
+ [CIDR] Fuller, V., Li, T., Yu, J. and K. Varadhan, "Classless
+ Inter-Domain Routing (CIDR): An Address Assignment and
+ Aggregation Strategy", RFC 1519, September 1993.
+
+ [ETHER] Crawford, M., "Transmission of IPv6 Packets over Ethernet
+ Networks", RFC 2464, December 1998.
+
+ [EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
+ Registration Authority",
+ http://standards.ieee.org/regauth/oui/tutorials/EUI64.html,
+ March 1997.
+
+ [FDDI] Crawford, M., "Transmission of IPv6 Packets over FDDI
+ Networks", RFC 2467, December 1998.
+
+ [MASGN] Hinden, R. and S. Deering, "IPv6 Multicast Address
+ Assignments", RFC 2375, July 1998.
+
+ [NSAP] Bound, J., Carpenter, B., Harrington, D., Houldsworth, J.
+ and A. Lloyd, "OSI NSAPs and IPv6", RFC 1888, August 1996.
+
+ [PRIV] Narten, T. and R. Draves, "Privacy Extensions for Stateless
+ Address Autoconfiguration in IPv6", RFC 3041, January 2001.
+
+ [TOKEN] Crawford, M., Narten, T. and S. Thomas, "Transmission of
+ IPv6 Packets over Token Ring Networks", RFC 2470, December
+ 1998.
+
+
+
+Hinden & Deering Standards Track [Page 19]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ [TRAN] Gilligan, R. and E. Nordmark, "Transition Mechanisms for
+ IPv6 Hosts and Routers", RFC 2893, August 2000.
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
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+Hinden & Deering Standards Track [Page 20]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+APPENDIX A: Creating Modified EUI-64 format Interface Identifiers
+
+ Depending on the characteristics of a specific link or node there are
+ a number of approaches for creating Modified EUI-64 format interface
+ identifiers. This appendix describes some of these approaches.
+
+Links or Nodes with IEEE EUI-64 Identifiers
+
+ The only change needed to transform an IEEE EUI-64 identifier to an
+ interface identifier is to invert the "u" (universal/local) bit. For
+ example, a globally unique IEEE EUI-64 identifier of the form:
+
+ |0 1|1 3|3 4|4 6|
+ |0 5|6 1|2 7|8 3|
+ +----------------+----------------+----------------+----------------+
+ |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
+ +----------------+----------------+----------------+----------------+
+
+ where "c" are the bits of the assigned company_id, "0" is the value
+ of the universal/local bit to indicate global scope, "g" is
+ individual/group bit, and "m" are the bits of the manufacturer-
+ selected extension identifier. The IPv6 interface identifier would
+ be of the form:
+
+ |0 1|1 3|3 4|4 6|
+ |0 5|6 1|2 7|8 3|
+ +----------------+----------------+----------------+----------------+
+ |cccccc1gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
+ +----------------+----------------+----------------+----------------+
+
+ The only change is inverting the value of the universal/local bit.
+
+Links or Nodes with IEEE 802 48 bit MAC's
+
+ [EUI64] defines a method to create a IEEE EUI-64 identifier from an
+ IEEE 48bit MAC identifier. This is to insert two octets, with
+ hexadecimal values of 0xFF and 0xFE, in the middle of the 48 bit MAC
+ (between the company_id and vendor supplied id). For example, the 48
+ bit IEEE MAC with global scope:
+
+
+
+
+
+
+
+
+
+
+
+
+Hinden & Deering Standards Track [Page 21]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ |0 1|1 3|3 4|
+ |0 5|6 1|2 7|
+ +----------------+----------------+----------------+
+ |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|
+ +----------------+----------------+----------------+
+
+ where "c" are the bits of the assigned company_id, "0" is the value
+ of the universal/local bit to indicate global scope, "g" is
+ individual/group bit, and "m" are the bits of the manufacturer-
+ selected extension identifier. The interface identifier would be of
+ the form:
+
+ |0 1|1 3|3 4|4 6|
+ |0 5|6 1|2 7|8 3|
+ +----------------+----------------+----------------+----------------+
+ |cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm|mmmmmmmmmmmmmmmm|
+ +----------------+----------------+----------------+----------------+
+
+ When IEEE 802 48bit MAC addresses are available (on an interface or a
+ node), an implementation may use them to create interface identifiers
+ due to their availability and uniqueness properties.
+
+Links with Other Kinds of Identifiers
+
+ There are a number of types of links that have link-layer interface
+ identifiers other than IEEE EIU-64 or IEEE 802 48-bit MACs. Examples
+ include LocalTalk and Arcnet. The method to create an Modified EUI-
+ 64 format identifier is to take the link identifier (e.g., the
+ LocalTalk 8 bit node identifier) and zero fill it to the left. For
+ example, a LocalTalk 8 bit node identifier of hexadecimal value 0x4F
+ results in the following interface identifier:
+
+ |0 1|1 3|3 4|4 6|
+ |0 5|6 1|2 7|8 3|
+ +----------------+----------------+----------------+----------------+
+ |0000000000000000|0000000000000000|0000000000000000|0000000001001111|
+ +----------------+----------------+----------------+----------------+
+
+ Note that this results in the universal/local bit set to "0" to
+ indicate local scope.
+
+Links without Identifiers
+
+ There are a number of links that do not have any type of built-in
+ identifier. The most common of these are serial links and configured
+ tunnels. Interface identifiers must be chosen that are unique within
+ a subnet-prefix.
+
+
+
+
+Hinden & Deering Standards Track [Page 22]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ When no built-in identifier is available on a link the preferred
+ approach is to use a global interface identifier from another
+ interface or one which is assigned to the node itself. When using
+ this approach no other interface connecting the same node to the same
+ subnet-prefix may use the same identifier.
+
+ If there is no global interface identifier available for use on the
+ link the implementation needs to create a local-scope interface
+ identifier. The only requirement is that it be unique within a
+ subnet prefix. There are many possible approaches to select a
+ subnet-prefix-unique interface identifier. These include:
+
+ Manual Configuration
+ Node Serial Number
+ Other node-specific token
+
+ The subnet-prefix-unique interface identifier should be generated in
+ a manner that it does not change after a reboot of a node or if
+ interfaces are added or deleted from the node.
+
+ The selection of the appropriate algorithm is link and implementation
+ dependent. The details on forming interface identifiers are defined
+ in the appropriate "IPv6 over <link>" specification. It is strongly
+ recommended that a collision detection algorithm be implemented as
+ part of any automatic algorithm.
+
+
+
+
+
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+Hinden & Deering Standards Track [Page 23]
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+APPENDIX B: Changes from RFC-2373
+
+ The following changes were made from RFC-2373 "IP Version 6
+ Addressing Architecture":
+
+ - Clarified text in section 2.2 to allow "::" to represent one or
+ more groups of 16 bits of zeros.
+ - Changed uniqueness requirement of Interface Identifiers from
+ unique on a link to unique within a subnet prefix. Also added a
+ recommendation that the same interface identifier not be assigned
+ to different machines on a link.
+ - Change site-local format to make the subnet ID field 54-bit long
+ and remove the 38-bit zero's field.
+ - Added description of multicast scop values and rules to handle the
+ reserved scop value 0.
+ - Revised sections 2.4 and 2.5.6 to simplify and clarify how
+ different address types are identified. This was done to insure
+ that implementations do not build in any knowledge about global
+ unicast format prefixes. Changes include:
+ o Removed Format Prefix (FP) terminology
+ o Revised list of address types to only include exceptions to
+ global unicast and a singe entry that identifies everything
+ else as Global Unicast.
+ o Removed list of defined prefix exceptions from section 2.5.6
+ as it is now the main part of section 2.4.
+ - Clarified text relating to EUI-64 identifiers to distinguish
+ between IPv6's "Modified EUI-64 format" identifiers and IEEE EUI-
+ 64 identifiers.
+ - Combined the sections on the Global Unicast Addresses and NSAP
+ Addresses into a single section on Global Unicast Addresses,
+ generalized the Global Unicast format, and cited [AGGR] and [NSAP]
+ as examples.
+ - Reordered sections 2.5.4 and 2.5.5.
+ - Removed section 2.7.2 Assignment of New IPv6 Multicast Addresses
+ because this is being redefined elsewhere.
+ - Added an IANA considerations section that updates the IANA IPv6
+ address allocations and documents the NSAP and AGGR allocations.
+ - Added clarification that the "IPv4-compatible IPv6 address" must
+ use global IPv4 unicast addresses.
+ - Divided references in to normative and non-normative sections.
+ - Added reference to [PRIV] in section 2.5.1
+ - Added clarification that routers must not forward multicast
+ packets outside of the scope indicated in the multicast address.
+ - Added clarification that routers must not forward packets with
+ source address of the unspecified address.
+ - Added clarification that routers must drop packets received on an
+ interface with destination address of loopback.
+ - Clarified the definition of IPv4-mapped addresses.
+
+
+
+Hinden & Deering Standards Track [Page 24]
+
+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+ - Removed the ABNF Description of Text Representations Appendix.
+ - Removed the address block reserved for IPX addresses.
+ - Multicast scope changes:
+ o Changed name of scope value 1 from "node-local" to
+ "interface-local"
+ o Defined scope value 4 as "admin-local"
+ - Corrected reference to RFC1933 and updated references.
+ - Many small changes to clarify and make the text more consistent.
+
+Authors' Addresses
+
+ Robert M. Hinden
+ Nokia
+ 313 Fairchild Drive
+ Mountain View, CA 94043
+ USA
+
+ Phone: +1 650 625-2004
+ EMail: hinden@iprg.nokia.com
+
+
+ Stephen E. Deering
+ Cisco Systems, Inc.
+ 170 West Tasman Drive
+ San Jose, CA 95134-1706
+ USA
+
+ Phone: +1 408 527-8213
+ EMail: deering@cisco.com
+
+
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+RFC 3513 IPv6 Addressing Architecture April 2003
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
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