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+<span class="pre noprint docinfo top">[<a href="http://tools.ietf.org/html/">RFCs/IDs</a>] [<a href="http://tools.ietf.org/rfc/rfc3513.txt">Plain Text</a>] [From <a href="http://tools.ietf.org/html/draft-ietf-ipngwg-addr-arch-v3">draft-ietf-ipngwg-addr-arch-v3</a>] </span><br>
+<span class="pre noprint docinfo"> </span><br>
+<span class="pre noprint docinfo">Obsoleted by: <a href="http://tools.ietf.org/html/rfc4291">4291</a> PROPOSED STANDARD</span><br>
+<span class="pre noprint docinfo"> </span><br>
+<pre>Network Working Group R. Hinden
+Request for Comments: 3513 Nokia
+Obsoletes: <a href="http://tools.ietf.org/html/rfc2373">2373</a> S. Deering
+Category: Standards Track Cisco Systems
+ April 2003
+
+
+ <span class="h1"><h1>Internet Protocol Version 6 (IPv6) Addressing Architecture</h1></span>
+
+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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 1]</span>
+<a name="page-2" id="page-2" href="#page-2"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+Table of Contents
+
+ <a href="#section-1">1</a>. Introduction.................................................<a href="#page-3">3</a>
+ <a href="#section-2">2</a>. IPv6 Addressing..............................................<a href="#page-3">3</a>
+ <a href="#section-2.1">2.1</a> Addressing Model.........................................<a href="#page-4">4</a>
+ <a href="#section-2.2">2.2</a> Text Representation of Addresses.........................<a href="#page-4">4</a>
+ <a href="#section-2.3">2.3</a> Text Representation of Address Prefixes..................<a href="#page-5">5</a>
+ <a href="#section-2.4">2.4</a> Address Type Identification..............................<a href="#page-6">6</a>
+ <a href="#section-2.5">2.5</a> Unicast Addresses........................................<a href="#page-7">7</a>
+ <a href="#section-2.5.1">2.5.1</a> Interface Identifiers..............................<a href="#page-8">8</a>
+ <a href="#section-2.5.2">2.5.2</a> The Unspecified Address............................<a href="#page-9">9</a>
+ <a href="#section-2.5.3">2.5.3</a> The Loopback Address...............................<a href="#page-9">9</a>
+ <a href="#section-2.5.4">2.5.4</a> Global Unicast Addresses..........................<a href="#page-10">10</a>
+ <a href="#section-2.5.5">2.5.5</a> IPv6 Addresses with Embedded IPv4 Addresses.......<a href="#page-10">10</a>
+ <a href="#section-2.5.6">2.5.6</a> Local-use IPv6 Unicast Addresses..................<a href="#page-11">11</a>
+ <a href="#section-2.6">2.6</a> Anycast Addresses.......................................<a href="#page-12">12</a>
+ <a href="#section-2.6.1">2.6.1</a> Required Anycast Address..........................<a href="#page-13">13</a>
+ <a href="#section-2.7">2.7</a> Multicast Addresses.....................................<a href="#page-13">13</a>
+ <a href="#section-2.7.1">2.7.1</a> Pre-Defined Multicast Addresses...................<a href="#page-15">15</a>
+ <a href="#section-2.8">2.8</a> A Node's Required Addresses.............................<a href="#page-17">17</a>
+ <a href="#section-3">3</a>. Security Considerations.....................................<a href="#page-17">17</a>
+ <a href="#section-4">4</a>. IANA Considerations.........................................<a href="#page-18">18</a>
+ <a href="#section-5">5</a>. References..................................................<a href="#page-19">19</a>
+ <a href="#section-5.1">5.1</a> Normative References....................................<a href="#page-19">19</a>
+ <a href="#section-5.2">5.2</a> Informative References..................................<a href="#page-19">19</a>
+ APPENDIX A: Creating Modified EUI-64 format Interface IDs......<a href="#page-21">21</a>
+ APPENDIX B: Changes from <a href="http://tools.ietf.org/html/rfc2373">RFC-2373</a>..............................<a href="#page-24">24</a>
+ Authors' Addresses.............................................<a href="#page-25">25</a>
+ Full Copyright Statement.......................................<a href="#page-26">26</a>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 2]</span>
+<a name="page-3" id="page-3" href="#page-3"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h2"><h2><a name="section-1">1</a>. Introduction</h2></span>
+
+ 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.
+
+<span class="h2"><h2><a name="section-2">2</a>. IPv6 Addressing</h2></span>
+
+ IPv6 addresses are 128-bit identifiers for interfaces and sets of
+ interfaces (where "interface" is as defined in <a href="#section-2">section 2</a> of [<a href="#ref-IPV6" title=""Internet Protocol, Version 6 (IPv6) Specification"">IPV6</a>]).
+ 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.
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 3]</span>
+<a name="page-4" id="page-4" href="#page-4"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h3"><h3><a name="section-2.1">2.1</a> Addressing Model</h3></span>
+
+ 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 <a href="#section-2.8">section 2.8</a> 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.
+
+<span class="h3"><h3><a name="section-2.2">2.2</a> Text Representation of Addresses</h3></span>
+
+ 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.
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 4]</span>
+<a name="page-5" id="page-5" href="#page-5"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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
+
+<span class="h3"><h3><a name="section-2.3">2.3</a> Text Representation of Address Prefixes</h3></span>
+
+ The text representation of IPv6 address prefixes is similar to the
+ way IPv4 addresses prefixes are written in CIDR notation [<a href="#ref-CIDR" title=""Classless Inter-Domain Routing (CIDR): An Address Assignment and Aggregation Strategy"">CIDR</a>]. 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 <a href="#section-2.2">section 2.2</a>.
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 5]</span>
+<a name="page-6" id="page-6" href="#page-6"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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
+
+<a href="#section-2.4">2.4</a> 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.
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 6]</span>
+<a name="page-7" id="page-7" href="#page-7"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ The general format of global unicast addresses is described in
+ <a href="#section-2.5.4">section 2.5.4</a>. Some special-purpose subtypes of global unicast
+ addresses which contain embedded IPv4 addresses (for the purposes of
+ IPv4-IPv6 interoperation) are described in <a href="#section-2.5.5">section 2.5.5</a>.
+
+ 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.
+
+<span class="h3"><h3><a name="section-2.5">2.5</a> Unicast Addresses</h3></span>
+
+ 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
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 7]</span>
+<a name="page-8" id="page-8" href="#page-8"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ from router to router, depending on what positions the router holds
+ in the routing hierarchy.
+
+<span class="h4"><h4><a name="section-2.5.1">2.5.1</a> Interface Identifiers</h4></span>
+
+ 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 [<a href="#ref-EUI64" title=""./rfc3513"">EUI64</a>]) 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 [<a href="#ref-PRIV" title=""Privacy Extensions for Stateless Address Autoconfiguration in IPv6"">PRIV</a>]).
+
+ 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
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 8]</span>
+<a name="page-9" id="page-9" href="#page-9"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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" [<a href="#ref-ETHER" title=""Transmission of IPv6 Packets over Ethernet Networks"">ETHER</a>], "IPv6 over FDDI" [<a href="#ref-FDDI" title=""Transmission of IPv6 Packets over FDDI Networks"">FDDI</a>], etc.
+
+<span class="h4"><h4><a name="section-2.5.2">2.5.2</a> The Unspecified Address</h4></span>
+
+ 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.
+
+<span class="h4"><h4><a name="section-2.5.3">2.5.3</a> The Loopback Address</h4></span>
+
+ 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.
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 9]</span>
+<a name="page-10" id="page-10" href="#page-10"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h4"><h4><a name="section-2.5.4">2.5.4</a> Global Unicast Addresses</h4></span>
+
+ 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 <a href="#section-2.5.1">section 2.5.1</a>.
+
+ 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 <a href="#section-2.5.1">section 2.5.1</a>. 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 [<a href="#ref-NSAP" title=""OSI NSAPs and IPv6"">NSAP</a>]. 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 [<a href="#ref-AGGR" title=""An Aggregatable Global Unicast Address Format"">AGGR</a>].
+
+<span class="h4"><h4><a name="section-2.5.5">2.5.5</a> IPv6 Addresses with Embedded IPv4 Addresses</h4></span>
+
+ The IPv6 transition mechanisms [<a href="#ref-TRAN" title=""Transition Mechanisms for IPv6 Hosts and Routers"">TRAN</a>] 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:
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 10]</span>
+<a name="page-11" id="page-11" href="#page-11"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ | 80 bits | 16 | 32 bits |
+ +--------------------------------------+--------------------------+
+ |0000..............................0000|FFFF| IPv4 address |
+ +--------------------------------------+----+---------------------+
+
+<span class="h4"><h4><a name="section-2.5.6">2.5.6</a> Local-Use IPv6 Unicast Addresses</h4></span>
+
+ 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.
+
+
+
+
+
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 11]</span>
+<a name="page-12" id="page-12" href="#page-12"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h3"><h3><a name="section-2.6">2.6</a> Anycast Addresses</h3></span>
+
+ 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 [<a href="#ref-ANYCST" title=""Host Anycasting Service"">ANYCST</a>]. Until more experience
+ has been gained and solutions are specified, the following
+ restrictions are imposed on IPv6 anycast addresses:
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 12]</span>
+<a name="page-13" id="page-13" href="#page-13"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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.
+
+<span class="h4"><h4><a name="section-2.6.1">2.6.1</a> Required Anycast Address</h4></span>
+
+ 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.
+
+<span class="h3"><h3><a name="section-2.7">2.7</a> Multicast Addresses</h3></span>
+
+ 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|
+ +-+-+-+-+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 13]</span>
+<a name="page-14" id="page-14" href="#page-14"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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.
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 14]</span>
+<a name="page-15" id="page-15" href="#page-15"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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.
+
+<span class="h4"><h4><a name="section-2.7.1">2.7.1</a> Pre-Defined Multicast Addresses</h4></span>
+
+ 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.
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 15]</span>
+<a name="page-16" id="page-16" href="#page-16"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 16]</span>
+<a name="page-17" id="page-17" href="#page-17"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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.
+
+<span class="h3"><h3><a name="section-2.8">2.8</a> A Node's Required Addresses</h3></span>
+
+ 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 <a href="#section-2.7.1">section 2.7.1</a>.
+ 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 <a href="#section-2.7.1">section 2.7.1</a>.
+
+<span class="h2"><h2><a name="section-3">3</a>. Security Considerations</h2></span>
+
+ IPv6 addressing documents do not have any direct impact on Internet
+ infrastructure security. Authentication of IPv6 packets is defined
+ in [<a href="#ref-AUTH" title=""IP Authentication Header"">AUTH</a>].
+
+
+
+
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 17]</span>
+<a name="page-18" id="page-18" href="#page-18"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h2"><h2><a name="section-4">4</a>. IANA Considerations</h2></span>
+
+ The table and notes at <a href="http://www.isi.edu/in-notes/iana/assignments/ipv6-address-space.txt">http://www.isi.edu/in-</a>
+ <a href="http://www.isi.edu/in-notes/iana/assignments/ipv6-address-space.txt">notes/iana/assignments/ipv6-address-space.txt</a> 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 [<a href="http://tools.ietf.org/html/rfc1888">RFC1888</a>]
+ Unassigned 0000 01 1/64
+ Unassigned 0000 1 1/32
+ Unassigned 0001 1/16
+ Global Unicast 001 1/8 [<a href="http://tools.ietf.org/html/rfc2374">RFC2374</a>]
+ 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.
+
+
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 18]</span>
+<a name="page-19" id="page-19" href="#page-19"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+<span class="h2"><h2><a name="section-5">5</a>. References</h2></span>
+
+<span class="h3"><h3><a name="section-5.1">5.1</a> Normative References</h3></span>
+
+ [<a name="ref-IPV6" id="ref-IPV6">IPV6</a>] Deering, S. and R. Hinden, "Internet Protocol, Version 6
+ (IPv6) Specification", <a href="http://tools.ietf.org/html/rfc2460">RFC 2460</a>, December 1998.
+
+ [<a name="ref-RFC2026" id="ref-RFC2026">RFC2026</a>] Bradner, S., "The Internet Standards Process -- Revision
+ 3", <a href="http://tools.ietf.org/html/bcp9">BCP 9</a> , <a href="http://tools.ietf.org/html/rfc2026">RFC 2026</a>, October 1996.
+
+<span class="h3"><h3><a name="section-5.2">5.2</a> Informative References</h3></span>
+
+ [<a name="ref-ANYCST" id="ref-ANYCST">ANYCST</a>] Partridge, C., Mendez, T. and W. Milliken, "Host Anycasting
+ Service", <a href="http://tools.ietf.org/html/rfc1546">RFC 1546</a>, November 1993.
+
+ [<a name="ref-AUTH" id="ref-AUTH">AUTH</a>] Kent, S. and R. Atkinson, "IP Authentication Header", <a href="http://tools.ietf.org/html/rfc2402">RFC</a>
+ <a href="http://tools.ietf.org/html/rfc2402">2402</a>, November 1998.
+
+ [<a name="ref-AGGR" id="ref-AGGR">AGGR</a>] Hinden, R., O'Dell, M. and S. Deering, "An Aggregatable
+ Global Unicast Address Format", <a href="http://tools.ietf.org/html/rfc2374">RFC 2374</a>, July 1998.
+
+ [<a name="ref-CIDR" id="ref-CIDR">CIDR</a>] Fuller, V., Li, T., Yu, J. and K. Varadhan, "Classless
+ Inter-Domain Routing (CIDR): An Address Assignment and
+ Aggregation Strategy", <a href="http://tools.ietf.org/html/rfc1519">RFC 1519</a>, September 1993.
+
+ [<a name="ref-ETHER" id="ref-ETHER">ETHER</a>] Crawford, M., "Transmission of IPv6 Packets over Ethernet
+ Networks", <a href="http://tools.ietf.org/html/rfc2464">RFC 2464</a>, December 1998.
+
+ [<a name="ref-EUI64" id="ref-EUI64">EUI64</a>] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
+ Registration Authority",
+ <a href="http://standards.ieee.org/regauth/oui/tutorials/EUI64.html">http://standards.ieee.org/regauth/oui/tutorials/EUI64.html</a>,
+ March 1997.
+
+ [<a name="ref-FDDI" id="ref-FDDI">FDDI</a>] Crawford, M., "Transmission of IPv6 Packets over FDDI
+ Networks", <a href="http://tools.ietf.org/html/rfc2467">RFC 2467</a>, December 1998.
+
+ [<a name="ref-MASGN" id="ref-MASGN">MASGN</a>] Hinden, R. and S. Deering, "IPv6 Multicast Address
+ Assignments", <a href="http://tools.ietf.org/html/rfc2375">RFC 2375</a>, July 1998.
+
+ [<a name="ref-NSAP" id="ref-NSAP">NSAP</a>] Bound, J., Carpenter, B., Harrington, D., Houldsworth, J.
+ and A. Lloyd, "OSI NSAPs and IPv6", <a href="http://tools.ietf.org/html/rfc1888">RFC 1888</a>, August 1996.
+
+ [<a name="ref-PRIV" id="ref-PRIV">PRIV</a>] Narten, T. and R. Draves, "Privacy Extensions for Stateless
+ Address Autoconfiguration in IPv6", <a href="http://tools.ietf.org/html/rfc3041">RFC 3041</a>, January 2001.
+
+ [<a name="ref-TOKEN" id="ref-TOKEN">TOKEN</a>] Crawford, M., Narten, T. and S. Thomas, "Transmission of
+ IPv6 Packets over Token Ring Networks", <a href="http://tools.ietf.org/html/rfc2470">RFC 2470</a>, December
+ 1998.
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 19]</span>
+<a name="page-20" id="page-20" href="#page-20"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ [<a name="ref-TRAN" id="ref-TRAN">TRAN</a>] Gilligan, R. and E. Nordmark, "Transition Mechanisms for
+ IPv6 Hosts and Routers", <a href="http://tools.ietf.org/html/rfc2893">RFC 2893</a>, August 2000.
+
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+<a name="page-21" id="page-21" href="#page-21"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+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
+
+ [<a name="ref-EUI64" id="ref-EUI64">EUI64</a>] 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:
+
+
+
+
+
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+<span class="grey">Hinden & Deering Standards Track [Page 21]</span>
+<a name="page-22" id="page-22" href="#page-22"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ |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.
+
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 22]</span>
+<a name="page-23" id="page-23" href="#page-23"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ 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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+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+APPENDIX B: Changes from <a href="http://tools.ietf.org/html/rfc2373">RFC-2373</a>
+
+ The following changes were made from <a href="http://tools.ietf.org/html/rfc2373">RFC-2373</a> "IP Version 6
+ Addressing Architecture":
+
+ - Clarified text in <a href="#section-2.2">section 2.2</a> 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 <a href="#section-2.5.6">section 2.5.6</a>
+ as it is now the main part of <a href="#section-2.4">section 2.4</a>.
+ - 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 [<a href="#ref-AGGR" title=""An Aggregatable Global Unicast Address Format"">AGGR</a>] and [<a href="#ref-NSAP" title=""OSI NSAPs and IPv6"">NSAP</a>]
+ as examples.
+ - Reordered sections 2.5.4 and 2.5.5.
+ - Removed <a href="#section-2.7.2">section 2.7.2</a> 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 [<a href="#ref-PRIV" title=""Privacy Extensions for Stateless Address Autoconfiguration in IPv6"">PRIV</a>] in <a href="#section-2.5.1">section 2.5.1</a>
+ - 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.
+
+
+
+<span class="grey">Hinden & Deering Standards Track [Page 24]</span>
+<a name="page-25" id="page-25" href="#page-25"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+ - 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 <a href="http://tools.ietf.org/html/rfc1933">RFC1933</a> 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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+<span class="grey">Hinden & Deering Standards Track [Page 25]</span>
+<a name="page-26" id="page-26" href="#page-26"><span class="break"> </span></a>
+<span class="grey"><a href="http://tools.ietf.org/html/rfc3513">RFC 3513</a> IPv6 Addressing Architecture April 2003</span>
+
+
+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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+<span class="break"> </span>
+
+</pre><br>
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