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General
The IEEE defined 64-bit extended unique identifier (EUI-64) is a concatenation of a 24-bit Organizationally Unique Identifier (OUI) value administered by the IEEE Registration Authority and a 40-bit extension identifier assigned by the organization with that OUI assignment.
The IEEE administers the assignment of 24-bit OUI values. The assignments of these values are public, so that a user of an EUI-64™ value can identify the manufacturer that provided the value[1]. The IEEE has no control over the assignments of 40-bit extension identifiers and assumes no liability for assignments of duplicate EUI-64 identifiers assigned by manufacturers.
Application restrictions
Given the minimal probability of consuming all the EUI-64 identifiers, the IEEE/RAC places minimal restrictions on their use within standards. Their major use is to distinctively identify hardware instances of devices.
They may also be used for other purposes where a unique identifier is desired. However, they may not be used to identify autonomously generated objects such as:
However, EUI-64 identifiers could be concatenated with a locally managed 64-bit identifier to create distinct 128-bit (or larger) unique object or file identifiers. Such use is not discouraged.
The IEEE/RAC reviews draft IEEE standards for correctness and clarity of EUI-64 usage. The IEEE/RAC does not restrict the use of EUI-64 identifiers within standards, if the standard conforms to the aforementioned restrictions. If the EUI-64 is referenced within non-IEEE standards, there shall not be any reference to IEEE unless approved by the IEEE/RAC. The main purpose of IEEE/RAC review is to ensure sufficiently efficient usage of assigned address spaces.
Usage restrictions
The EUI-64 is a trademarked IEEE term and there are a number of restrictions on EUI-64 usage; see <<application form>> for details. These restrictions are subject to change on a per-purchase basis.
Application documentation
As a condition for receiving an OUI assignment, a manufacturer of EUI-64 values accepts the following responsibilities:
Manufacturer-assigned identifiers
The manufacturer identifier assignment allows the assignee to generate approximately 1 trillion (1012) unique EUI-64 values, by varying the last 40 bits. The IEEE intends not to assign another OUI value to a manufacturer of EUI-64 values until the manufacturer has consumed, in product, the preponderance (more than 90%) of this block. It is incumbent upon the manufacturer to ensure that large portions of the block are not left unused in the consumption process.
64-BIT EXTENDED UNIQUE IDENTIFIER FORMAT TUTORIAL
Byte sequence formats
You may have a 64-bit global identifier (EUI-64) provided by an authorized manufacturer of these values (in the form of electronically readable chips). A 24-bit first portion of this value is the OUI value assigned to the manufacturer by the IEEE Registration Authority. A 40-bit second portion of this identifier is assigned by the manufacturer.
For example, assume that a manufacturer's IEEE-assigned OUI value is AC-DE-48 and the manufacturer-selected extension identifier for a given component is 23-45-67-AB-CD. The EUI-64 value generated from these two numbers is AC-DE-48-23-45-67-AB-CD.
Some standards specify an EUI-64 by a string of eight bytes, labeled here as eui[0] through eui[7]. For those standards, the format of the EUI-64 is illustrated below. Although different standards may specify different bit-transmission orders, bytes are normally transmitted in an ascending index-value order.
Value: AC-DE-48-23-45-67-AB-CD
| OUI | extension identifier | field
| | |
| eui[0] | eui[1] | eui[2] | eui[3] | eui[4] | eui[5] | eui[6] | eui[7] | order
| | | | | | | | |
| AC | DE | 48 | 23 | 45 | 67 | AB | CD | hex
Numerical formats
Other standards specify an EUI-64 to be a numerical value, upon which computations (such as base/bounds or bit selections) can be performed. For those standards, the format of the EUI-64 is illustrated below:
Value: ACDE48234567ABCD16
| OUI | extension identifier | field
| | |
| AC | DE | 48 | 23 | 45 | 67 | AB | CD | hex
Restricted encapsulated values
To support encapsulation of EUI-48™ and MAC-48 values within small subsets of the EUI-64 values, the first two bytes of the manufacturer's extension identifier must not be FF-FF or FF-FE. Thus, the 64-bit values of the following form are never assigned EUI-64 values:
XX-XX-XX-FF-FE-YY-YY-YY (an EUI-48 extension)
XX-XX-XX-FF-FF-YY-YY-YY (a MAC-48 extension[deprecated])
The letters 'X' and 'Y' represent hexadecimal digits and show how the EUI-48 value can be unambiguously encapsulated within the EUI-64 value; the 'X' and 'Y' digits represent the OUI and extension-identifier portions of the EUI-48/MAC-48 values, respectively.
This allows EUI-48 identifiers to be encapsulated and transported as (otherwise unassigned) EUI-64 identifiers. The intent is to enable migration to a single form of OUI based globally unique 64-bit identifiers.
An EUI-48 identifier can be encapsulated and placed within an EUI-64 container. For example, assume that a manufacturer's IEEE-assigned OUI value is AC-DE-48 and the manufacturer-selected extension identifier for a given item is 23-45-67. The EUI-48 value generated from these two numbers is AC-DE-48-23-45-67, whose byte representationn is illustrated below:
EUI-48 value: AC-DE-48-23-45-67
| OUI | extension identifier | field
| | |
| AC | DE | 48 | 23 | 45 | 67 | hex
An EUI-64 value is generated by concatenating OUI, FF-FE, and extension-identifier values. The byte representation for this EUI-64 value is illustrated below:
Encapsulating EUI-64 value: AC-DE-48-FF-FE-23-45-67
| OUI | EUI label | extension identifier | field
| | | |
| AC | DE | 48 | FF | FE | 23 | 45 | 67 | hex
Encapsulated MAC-48 values [deprecated]
A MAC-48 identifier can be encapsulated and placed within an EUI-64 container. For example, assume that a manufacturer's IEEE-assigned OUI value is AC-DE-48 and the manufacturer-selected extension identifier for a given item is 23-45-67. The EUI-48 value generated from these two numbers is AC-DE-48-23-45-67, whose byte representation is illustrated below:
EUI-48 value: AC-DE-48-23-45-67
| OUI | extension identifier | field
| | |
| AC | DE | 48 | 23 | 45 | 67 | hex
An EUI-64 value is generated by concatenating OUI, FF-FE, and extension-identifier values. The byte representation for this EUI-64 value is illustrated below:
Encapsulating EUI-64 value: AC-DE-48-FF-FF-23-45-67
| OUI | EUI label | extension identifier | field
| | | |
| AC | DE | 48 | FF | FF | 23 | 45 | 67 | hex
Encapsulated EUI-60 values
An EUI-60 identifier can be encapsulated and placed within an EUI-64 container. For example, assume that a manufacturer's IEEE-assigned OUI value is AC-DE-48 and the manufacturer-selected extension identifier for a given item is 2.3.4.5..6.7.A.B.C. The EUI-60 value generated from these two numbers is AC-DE-48:2.3.4.5.6.7.A.B.C, whose nibble representation is illustrated below:
EUI-60 value: AC-DE-48:2.3.4.5.6.7.A.B.C
| OUI | extension identifier | field
| | |
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | nibble
A C D E 4 8 2 3 4 5 6 7 A B C | hex
An encapsulating EUI-64 value is generated by appending the EUI-60 with a 4-bit zero value, as illustrated below:
Encapsulating EUI-64 value: AC-DE-48-23-45-67-AB-C0
| OUI | extension identifier | field
| | | |
| AC | DE | 48 | 23 | 45 | 67 | AB | C0 | hex
Unassigned EUI-64 values
The all-zeros and all-ones EUI-64 values will never be assigned and may be used to represent NULL EUI-64 address values. As an example, either of these values could represent an uninitialized value, before that location is accessible or properly initialized by hardware/firmware. Similarly, either value could represent invalid, when an optional EUI-64 value is not supplied.
[1]Except for private OUI values, where the owner of the OUI value is confidential. These remain private.
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