Organizationally Unique Identifier
Encyclopedia
An Organizationally Unique Identifier (OUI) is a 24-bit number that is purchased from the Institute of Electrical and Electronics Engineers, Incorporated
(IEEE) Registration Authority
. This identifier uniquely identifies a vendor, manufacturer, or other organization (referred to by the IEEE as the “assignee”) globally or worldwide and effectively reserves a block of each possible type of derivative identifier (such as MAC address
es, group addresses
, Subnetwork Access Protocol
protocol identifiers, etc.) for the exclusive use of the assignee. The OUI is subsequently used by the assignee to create particular instances of these identifiers for various purposes, such as the identification of a particular piece of equipment (e.g., a network interface controller (NIC)) or the identification of a network protocol, and for use in various computer hardware
products, including MAC addresses for Ethernet
and other NICs
(network interface cards
), World Wide Name
s for Fibre Channel
host bus adapters, and other Fibre Channel and Serial Attached SCSI
devices.
In MAC addresses, the OUI is combined with a 24-bit number (assigned by the owner or 'assignee' of the OUI) to form the address. The first three octet
s of the address are the OUI.
).
es)
Note: It is interesting to note that the bit-reversed representation corresponds to the convention of transmitting the least-significant-bit
of each byte
first in serial data communications
.
Example:
An OUI consisting of the hexadecimal digits ACDE4816 would be represented as follows:
command. Canonical form is the intended standard.
However, since 802.3
(Ethernet) and 802.4 (Token Bus) send the bits over the wire with least significant bit first, while 802.5 (Token Ring) and 802.6
(FDDI) send the bits over the wire with most significant bit first, confusion may arise where an OUI in the latter scenario is represented with bits reversed from the canonical representation. So for instance, an OUI whose canonical form is
The two least-significant-bits of the second nibble
of the first octet of the hexadecimal representation (i.e., the two least significant bits of the first octet) of the OUI are reserved as flag bits for some protocols (e.g., 'M' bit and 'X' bit), flags to indicate whether the address is part of an individual (unicast) or group (multicast) address block (e.g., Individual / Group [I / G] bit or Unicast / Multicast [U / M] bit), flags to indicate whether an address is universally or locally administered (e.g., Universal / Local [U / L] bit), etc., and should not contain the values 1,2,3,5,6,7,9,a, b,d, e, or f, unless these values reflect the true meaning of these flag bits – if the organization that owns the OUI does set one of these bits when creating an identifier, then the value of the second nibble of the first octet changes accordingly in representations of the OUI (e.g., if the hexadecimal value of the second nibble of the first octet is 'C' and the least-significant-bit is set, then the value becomes 'D').
Note: “Three-octet values occupying the same fields as OUIs can occupy, but with the next-to-LSB of the first octet set to 1, are locally assigned and have no relationship to the IEEE-assigned values...”.
Example:
The following figure shows the position of these bits in significance order:
Note: The OUI of AC-DE-48 is used for illustrative purposes only and this information applies regardless of the actual value of the OUI.
Notes:
Note: This identifier was previously used as the world wide name (WWN) identifier within some storage systems. Its use is now considered deprecated by the IEEE and the EUI-64 identifier should be used in the future for this and all other purposes for which the EUI-60 was previously used. Some of the storage systems in which an OUI based variant was used are Fibre Channel
, and Serial Attached SCSI
(SAS).
Note: According to the IEEE guidelines, the first four digits of the organizationally assigned identifier (i.e., the first four digits of the extension identifier) portion of an EUI-64 “shall not be FFFE16 or FFFF16” (i.e., EUI-64 identifiers of the form ccccccFFFEeeeeee and ccccccFFFFeeeeee are not allowed) – this is to support the encapsulation of EUI-48 and MAC-48 values into EUI-64 values.
uses a 64-bit Modified Extended Unique Identifier (Modified EUI-64) in the lower half of some IPv6 addresses. A Modified EUI-64 is an EUI-64 with the U/L bit inverted.
There are other identifiers that may be formed using the OUI but those listed above are the most commonly used.
Encapsulation of MAC-48 within EUI-64 Example:
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the MAC-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this MAC-48 identifier has the following binary transmission order:
The same MAC-48 identifier after encapsulation within an EUI-64 has the following transmission order:
The same MAC-48 identifier after encapsulation within an EUI-64 has the following significance order:
Encapsulation of EUI-48 within EUI-64 Example:
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the EUI-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this EUI-48 identifier has the following format in significance order:
The same EUI-48 identifier after encapsulation within an EUI-64 has the following format in significance order:
Encapsulation of MAC-48 or EUI-48 within Modified EUI-64 Example:
In the encapsulation within a Modified EUI-64 a MAC-48 is treated as an EUI-48 and the U/L bit is inverted.
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the MAC-48 or EUI-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this MAC-48 or EUI-48 identifier has the following format in significance order:
The same MAC-48 or EUI-48 identifier after encapsulation within a Modified EUI-64 has the following format in significance order:
(IAB) is a block of identifiers that is formed by concatenating a 24-bit Organizationally Unique Identifier (OUI) that is owned by the IEEE Registration Authority with an additional 12-bit extension identifier that is assigned by the IEEE Registration Authority and then reserving an additional 12 bits for use by the assignee. The resulting 48-bit identifier uniquely identifies the assignee of the IAB and provides 4096 unique EUI-48 numbers for use by the organization that purchased the IAB. The assignee may create unique identifiers by concatenating a 12-bit extension identifier that is assigned by the organization that purchases the IAB in the bit positions occupied by the 12 additional bits mentioned previously. The purpose of the IAB is to allow organizations to purchase smaller blocks of identifiers.
The IEEE Registration Authority distinguishes between IABs and OUI-36 values. Both are 36-bit values which may be used to generate EUI-48 values, but IABs may not be used to generate EUI-64 values.
Example of EUI-48 created within an IAB: An EUI-48 identifier is formed by combining the 36-bit IEEE assigned IAB base value with a 12-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 12-bit extension identifier is hhh16, then the EUI-48 value generated by combining these two numbers is FF-FF-FF-FF-Fh-hh.
Note:There are also IAB based CDI-40 sequences that are formed by combining the 36-bit IEEE assigned IAB base value with the 4-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 4-bit extension identifier is 0h16, then the CDI-40 value generated by combining these two numbers is FF-FF-FF-FF-Fh.
Institute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
(IEEE) Registration Authority
IEEE Registration Authority
The IEEE Registration Authority is the administrative body that is responsible for registering and administering Organizationally Unique Identifiers and other types of identifiers which are used in the computer and electronics industries The...
. This identifier uniquely identifies a vendor, manufacturer, or other organization (referred to by the IEEE as the “assignee”) globally or worldwide and effectively reserves a block of each possible type of derivative identifier (such as MAC address
MAC address
A Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
es, group addresses
MAC address
A Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
, Subnetwork Access Protocol
Subnetwork Access Protocol
The Subnetwork Access Protocol is a mechanism for multiplexing, on networks using IEEE 802.2 LLC, more protocols than can be distinguished by the 8-bit 802.2 Service Access Point fields. SNAP supports identifying protocols by Ethernet type field values; it also supports vendor-private protocol...
protocol identifiers, etc.) for the exclusive use of the assignee. The OUI is subsequently used by the assignee to create particular instances of these identifiers for various purposes, such as the identification of a particular piece of equipment (e.g., a network interface controller (NIC)) or the identification of a network protocol, and for use in various computer hardware
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
products, including MAC addresses for Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
and other NICs
Network card
A network interface controller is a computer hardware component that connects a computer to a computer network....
(network interface cards
Network card
A network interface controller is a computer hardware component that connects a computer to a computer network....
), World Wide Name
World Wide Name
A World Wide Name or World Wide Identifier is a unique identifier which identifies a particular Fibre Channel, Advanced Technology Attachment or Serial Attached SCSI target...
s for Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
host bus adapters, and other Fibre Channel and Serial Attached SCSI
Serial Attached SCSI
Serial Attached SCSI is a computer bus used to move data to and from computer storage devices such as hard drives and tape drives. SAS depends on a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in data centers and workstations,...
devices.
In MAC addresses, the OUI is combined with a 24-bit number (assigned by the owner or 'assignee' of the OUI) to form the address. The first three octet
Octet
-Music:* Octet , ensemble consisting of eight instruments or voices, or composition written for such an ensemble* Octet , 1793 composition by Ludwig van Beethoven* Octet , 1825 composition by Felix Mendelssohn...
s of the address are the OUI.
Representational and Formatting Conventions / Standards (IEEE 802-2001)
The following terms are defined (either implicitly or explicitly) in IEEE Standard 802-2001 for use in referring to the various representations and formats of OUIs and the identifiers that may be created using them.Hexadecimal Representation
“The representation of a sequence of octet values in which the values of the individual octets are displayed in order from left to right, with each octet value represented as a two-digit hexadecimal numeral, and with the resulting pairs of hexadecimal digits separated by hyphens. The order of the hexadecimal digits in each pair, and the mapping between the hexadecimal digits and the bits of the octet value, are derived by interpreting the bits of the octet value as a binary numeral using the normal mathematical rules for digit significance.” (See hexadecimalHexadecimal
In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...
).
Canonical Format
“The format of a MAC data frame in which the octets of any MAC addresses conveyed in the MAC user data field have the same bit ordering as in the Hexadecimal Representation.” (See MAC data frame, MAC addressMAC address
A Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
es)
Significance Order
This appears from the context of the IEEE Standard 802-2001 to be another term for the 'Hexadecimal Representation' – i.e., “by interpreting the bits of the octet value as a binary numeral using the normal mathematical rules for digit significance.”Bit-Reversed Representation
“The representation of a sequence of octet values in which the values of the individual octets are displayed in order from left to right, with each octet value represented as a two-digit hexadecimal numeral, and with the resulting pairs of hexadecimal digits separated by colons. The order of the hexadecimal digits in each pair, and the mapping between the hexadecimal digits and the bits of the octet value, are derived by reversing the order of the bits in the octet value and interpreting the resulting bit sequence as a binary numeral using the normal mathematical rules for digit significance.”Note: It is interesting to note that the bit-reversed representation corresponds to the convention of transmitting the least-significant-bit
Least significant bit
In computing, the least significant bit is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The lsb is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digits...
of each byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
first in serial data communications
Serial communications
In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels...
.
Noncanonical Representation
“The format of a MAC data frame in which the octets of MAC addresses conveyed in the MAC user data field have the same bit ordering as in the Bit-reversed representation.”Transmission Order
The order in which an octet or a sequence of octets is transmitted over the transmission medium – this order normally corresponds to the bit-reversed representation.Example:
An OUI consisting of the hexadecimal digits ACDE4816 would be represented as follows:
Hexadecimal / Canonical format:
AC-DE-48
| OUI |
| Octet 0 | Octet 1 | Octet 2 |
| A C | D E | 4 8 |
|1010 1100|1101 1110|0100 1000|
Bit-reversed / Noncanonical format:
35:7B:12
| OUI |
| Octet 0 | Octet 1 | Octet 2 |
| 3 5 | 7 B | 1 2 |
|0011 0101|0111 1011|0001 0010|
Potential for Confusion in Token Ring Settings
Ethernet users are used to seeing canonical form, such as in the output of the ifconfigIfconfig
ifconfig is a system administration utility in Unix-like operating systems to configure, control, and query TCP/IP network interface parameters from a command line interface or in system configuration scripts...
command. Canonical form is the intended standard.
However, since 802.3
IEEE 802.3
IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...
(Ethernet) and 802.4 (Token Bus) send the bits over the wire with least significant bit first, while 802.5 (Token Ring) and 802.6
IEEE 802.6
IEEE 802.6 is a standard governed by the ANSI for Metropolitan Area Networks . It is an improvement of an older standard which used the Fiber distributed data interface network structure. The FDDI-based standard failed due to its expensive implementation and lack of compatibility with current LAN...
(FDDI) send the bits over the wire with most significant bit first, confusion may arise where an OUI in the latter scenario is represented with bits reversed from the canonical representation. So for instance, an OUI whose canonical form is
ACDE48 could be seen written as 357B12 if translation is done improperly or inconsistently. The latter form (Bit-Reversed or Noncanonical representation), may also be referred to in the literature as "MSB format", "IBM format", or "Token Ring format" for this reason. RFC2469 explains the problem in more detail.Format
The OUI is normally discussed and represented as a set of octets in hexadecimal notation separated by dashes (i.e., FF-FF-FF) or as a set of octets separated by colons in bit-reversed notation (i.e., FF:FF:FF).The two least-significant-bits of the second nibble
Nibble
In computing, a nibble is a four-bit aggregation, or half an octet...
of the first octet of the hexadecimal representation (i.e., the two least significant bits of the first octet) of the OUI are reserved as flag bits for some protocols (e.g., 'M' bit and 'X' bit), flags to indicate whether the address is part of an individual (unicast) or group (multicast) address block (e.g., Individual / Group [I / G] bit or Unicast / Multicast [U / M] bit), flags to indicate whether an address is universally or locally administered (e.g., Universal / Local [U / L] bit), etc., and should not contain the values 1,2,3,5,6,7,9,a, b,d, e, or f, unless these values reflect the true meaning of these flag bits – if the organization that owns the OUI does set one of these bits when creating an identifier, then the value of the second nibble of the first octet changes accordingly in representations of the OUI (e.g., if the hexadecimal value of the second nibble of the first octet is 'C' and the least-significant-bit is set, then the value becomes 'D').
Note: “Three-octet values occupying the same fields as OUIs can occupy, but with the next-to-LSB of the first octet set to 1, are locally assigned and have no relationship to the IEEE-assigned values...”.
Example:
The following figure shows the position of these bits in significance order:
| OUI |
| Octet 0 | Octet 1 | Octet 2 |
| nibble | nibble | nibble |
| __||__ | __||__ | __||__ |
| | | | | | | | | |
| 0 || 1 | 2 || 3 | 4 || 5 |
|bits||bits|bits||bits|bits||bits|
|7654||3210|7654||3210|7654||3210|
||||| ||||||||| ||||||||| |||||
| A C | D E | 4 8 |
|1010 1100|1101 1110|0100 1000|
| | || | |
| | || | least-significant-bit of OUI
| | || least-significant-byte of OUI
| | |least-significant-bit of first octet of OUI = I/G or M bit
| | next-to-least-significant-bit of first octet of OUI = U/L or X bit
| most-significant-byte of OUI
most-significant-bit of OUI
Note: The OUI of AC-DE-48 is used for illustrative purposes only and this information applies regardless of the actual value of the OUI.
Notes:
- The IEEE also refers to the OUI as 'company_id' when the OUI is written as a base 16 number (i.e., as a hexadecimal number with no dashes or colons separating the octets of the OUI).
- In the following, 'F' and 'h' represent any hexadecimal number.
- In the following, 'c' represents the digits of the 'company_id', and 'e' represents the digits of the extension identifier supplied by the organization to whom the OUI is registered.
32-bit Context Dependent Identifier (CDI-32)
The CDI-32 is an identifier that is formed by concatenating the 24-bit OUI with an 8-bit extension identifier that is assigned by the organization that purchased the OUI – the resulting identifier is generally represented as a set of octets separated by dashes (hexadecimal notation) or colons (bit-reversed notation) as in FF-FF-FF-FF or FF:FF:FF:FF, as a string of 4 bytes as in {FF,FF,FF,FF}, or as a base 16 number as in FFFFFFFF16.40-bit Context Dependent Identifier (CDI-40)
The CDI-40 is an identifier that is formed by concatenating the 24-bit OUI with a 16-bit extension or by concatenating a 36-bit OUI-36 with a 4-bit extension. In either case, the extension is assigned by the organization that purchased the OUI. The resulting identifier is generally represented as a set of octets separated by dashes (hexadecimal notation) or colons (bit-reversed notation) as in FF-FF-FF-FF-FF or FF:FF:FF:FF:FF, as a string of 5 bytes as in {FF,FF,FF,FF,FF}, or as a base 16 number as in FFFFFFFFFF16.48-bit Media Access Control Identifier (MAC-48)
The IEEE now considers the label MAC-48 to be an obsolete term which was previously used to refer to a specific type of EUI-48 identifier used to address hardware interfaces (e.g., Network Interface Controllers and other network hardware) within existing IEEE 802 based networking applications and should not be used in the future. Instead, the term EUI-48 should be used by manufacturers and others in the field for this purpose – i.e., this identifier is identical to the EUI-48 identifier and is an obsolete label for the same identifier, although some distinction is still made when encapsulating MAC-48 and EUI-48 identifiers within EUI-64 identifiers.48-bit Extended Unique Identifier (EUI-48)
The EUI-48 is an identifier that is formed by concatenating the 24-bit OUI with a 24-bit extension identifier that is assigned by the organization that purchased the OUI – the resulting identifier is generally represented as a set of octets separated by dashes (hexadecimal notation) or colons (bit-reversed notation) as in FF-FF-FF-FF-FF-FF or FF:FF:FF:FF:FF:FF, as a string of 6 bytes as in {FF,FF,FF,FF,FF,FF}, or as a base 16 number as in FFFFFFFFFFFF16.60-bit Extended Unique Identifier (EUI-60)
The EUI-60 is an identifier that is formed by concatenating the 24-bit OUI with a 36-bit extension identifier that is assigned by the organization that purchased the OUI – the resulting identifier is generally represented by a string of 15 nibbles, as a base 16 number as in FFFFFFFFFFFFFFF16, or as FF-FF-FF:F.F.F.F.F.F.F.F.F as an EUI-64 value.Note: This identifier was previously used as the world wide name (WWN) identifier within some storage systems. Its use is now considered deprecated by the IEEE and the EUI-64 identifier should be used in the future for this and all other purposes for which the EUI-60 was previously used. Some of the storage systems in which an OUI based variant was used are Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
, and Serial Attached SCSI
Serial Attached SCSI
Serial Attached SCSI is a computer bus used to move data to and from computer storage devices such as hard drives and tape drives. SAS depends on a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in data centers and workstations,...
(SAS).
64-bit Extended Unique Identifier (EUI-64)
The EUI-64 is an identifier that is formed by concatenating the 24-bit OUI with a 40-bit extension identifier that is assigned by the organization that purchased the OUI – the resulting identifier is generally represented as a set of octets separated by dashes (hexadecimal notation) or colons (bit-reversed notation) as in FF-FF-FF-FF-FF-FF-FF-FF or FF:FF:FF:FF:FF:FF:FF:FF, as a string of 8 bytes as in {FF,FF,FF,FF,FF,FF,FF,FF}, or as a base 16 number as in FFFFFFFFFFFFFFFF16.Note: According to the IEEE guidelines, the first four digits of the organizationally assigned identifier (i.e., the first four digits of the extension identifier) portion of an EUI-64 “shall not be FFFE16 or FFFF16” (i.e., EUI-64 identifiers of the form ccccccFFFEeeeeee and ccccccFFFFeeeeee are not allowed) – this is to support the encapsulation of EUI-48 and MAC-48 values into EUI-64 values.
Other Identifiers
IPv6IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
uses a 64-bit Modified Extended Unique Identifier (Modified EUI-64) in the lower half of some IPv6 addresses. A Modified EUI-64 is an EUI-64 with the U/L bit inverted.
There are other identifiers that may be formed using the OUI but those listed above are the most commonly used.
Encapsulating
Other identifiers, such as MAC-48 and EUI-48 values, can be contained within a larger identifier or 'container', such as EUI-64, by creating the larger identifier through a process of combining the smaller identifier with specified values placed in specified bit-positions within the larger identifier – this process is known as 'encapsulation' and is provided for the purpose of easing the transition from MAC-48 and EUI-48 to EUI-64 and to provide a mechanism for the conversion of MAC-48 and EUI-48 identifiers to EUI-64 in such a way that duplicate or conflicting values are avoided.Encapsulation of MAC-48 within EUI-64 Example:
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the MAC-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this MAC-48 identifier has the following binary transmission order:
| OUI | extension identifier | field
| 1st | 2nd | 3rd | 4th | 5th | 6th | octet
| C A | E D | 8 4 | 3 2 | 5 4 | 7 6 | hex
0011 0101 0111 1011 0001 0010 1100 0100 1010 0010 1110 0110 bits
| | | | | | | | | | | |
lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb
The same MAC-48 identifier after encapsulation within an EUI-64 has the following transmission order:
| OUI | MAC label | extension identifier | field
| 1st | 2nd | 3rd | 4th | 5th | 6th | 7th | 8th | order
| C A | E D | 8 4 | F F | F F | 3 2 | 5 4 | 7 6 | hex
00110101 01111011 00010010 11111111 11111111 11000100 10100100 11100110 bits
| | | | | | | | | | | | | | | |
lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb
The same MAC-48 identifier after encapsulation within an EUI-64 has the following significance order:
| OUI | MAC label | extension identifier | field
| AC | DE | 48 | FF | FF | 23 | 45 | 67 | hex
10101100 11011110 01001000 11111111 11111111 00100011 01000101 01100111 bits
| | | |
| most-significant-byte least-significant-byte |
most-significant-bit least-significant-bit
Encapsulation of EUI-48 within EUI-64 Example:
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the EUI-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this EUI-48 identifier has the following format in significance order:
| company_id | extension identifier | field
| AC | DE | 48 | 23 | 45 | 67 | hex
10101100 11011110 01001000 00100011 01000101 01100111 bits
| | | |
| most-significant-byte least-significant-byte |
most-significant-bit least-significant-bit
The same EUI-48 identifier after encapsulation within an EUI-64 has the following format in significance order:
| company_id | EUI label | extension identifier | field
| AC | DE | 48 | FF | FE | 23 | 45 | 67 | hex
10101100 11011110 01001000 11111111 11111110 00100011 01000101 01100111 bits
| | | |
| most-significant-byte least-significant-byte |
most-significant-bit least-significant-bit
Encapsulation of MAC-48 or EUI-48 within Modified EUI-64 Example:
In the encapsulation within a Modified EUI-64 a MAC-48 is treated as an EUI-48 and the U/L bit is inverted.
Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the MAC-48 or EUI-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this MAC-48 or EUI-48 identifier has the following format in significance order:
| company_id | extension identifier | field
| AC | DE | 48 | 23 | 45 | 67 | hex
10101100 11011110 01001000 00100011 01000101 01100111 bits
| | | |
| most-significant-byte least-significant-byte |
most-significant-bit least-significant-bit
The same MAC-48 or EUI-48 identifier after encapsulation within a Modified EUI-64 has the following format in significance order:
| company_id | EUI label | extension identifier | field
| AE | DE | 48 | FF | FE | 23 | 45 | 67 | hex
10101110 11011110 01001000 11111111 11111110 00100011 01000101 01100111 bits
| | | |
| most-significant-byte least-significant-byte |
most-significant-bit least-significant-bit
Individual Address Block
The Individual Address BlockIndividual Address Block
The Individual Address Block is a block of identifiers that is formed by concatenating a 24-bit Organizationally Unique Identifier that is owned by the IEEE Registration Authority with an additional 12-bit extension identifier that is assigned by the IEEE Registration Authority and then reserving...
(IAB) is a block of identifiers that is formed by concatenating a 24-bit Organizationally Unique Identifier (OUI) that is owned by the IEEE Registration Authority with an additional 12-bit extension identifier that is assigned by the IEEE Registration Authority and then reserving an additional 12 bits for use by the assignee. The resulting 48-bit identifier uniquely identifies the assignee of the IAB and provides 4096 unique EUI-48 numbers for use by the organization that purchased the IAB. The assignee may create unique identifiers by concatenating a 12-bit extension identifier that is assigned by the organization that purchases the IAB in the bit positions occupied by the 12 additional bits mentioned previously. The purpose of the IAB is to allow organizations to purchase smaller blocks of identifiers.
The IEEE Registration Authority distinguishes between IABs and OUI-36 values. Both are 36-bit values which may be used to generate EUI-48 values, but IABs may not be used to generate EUI-64 values.
Example of EUI-48 created within an IAB: An EUI-48 identifier is formed by combining the 36-bit IEEE assigned IAB base value with a 12-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 12-bit extension identifier is hhh16, then the EUI-48 value generated by combining these two numbers is FF-FF-FF-FF-Fh-hh.
Note:There are also IAB based CDI-40 sequences that are formed by combining the 36-bit IEEE assigned IAB base value with the 4-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 4-bit extension identifier is 0h16, then the CDI-40 value generated by combining these two numbers is FF-FF-FF-FF-Fh.
Compare to
- Globally Unique IdentifierGlobally Unique IdentifierA globally unique identifier is a unique reference number used as an identifier in computer software. The term GUID also is used for Microsoft's implementation of the Universally unique identifier standard....
(GUID) - Object identifierObject identifierIn computing, an object identifier or OID is an identifier used to name an object . Structurally, an OID consists of a node in a hierarchically-assigned namespace, formally defined using the ITU-T's ASN.1 standard. Successive numbers of the nodes, starting at the root of the tree, identify each...
(OID) - Private Enterprise numbersEnterprise numbersPrivate Enterprise Numbers are created and maintained by the Internet Assigned Number Authority in a public registry, including a publicly revealed email address and "contact name'. Any private enterprise may request, at no cost, a Private Enterprise Number to be assigned...
(PEN)
External links
- IEEE Registration Authority Tutorials
- IEEE Registration Authority - Frequently Asked Questions
- IEEE Public OUI and Company_id Assignment lookup
- IEEE Public OUI list
- IEEE Public IAB list
- IANA Considerations and IETF Protocol Usage for IEEE 802 Parameters
- IANA list of Ethernet Numbers
- WiresharkWiresharkWireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software and communications protocol development, and education...
's OUI Lookup Tool and MAC address list - MAC Find Vendor/Ethernet/Bluetooth MAC Address Lookup
- 8086 Tools' MAC Address Lookup
- NetLookup Fast and easy lookup using MAC address or vendor
- MACVendorLookup.com Find by a list of addresses
- Hardware Address (finds items not found in the above)