Unique identifier of the organization

A supplier or manufacturer of equipment ( or another organization that has contacted IEEE to assign an identifier ) is assigned a globally unique organization identifier (OUI) ^{[2] [3]} , and thus a block of all kinds of derived identifiers , such as MAC addresses, is reserved for this organization , multicast MAC addresses, SNAP identifiers, etc.

Further, the OUI is used by this organization to create its own identifiers on its basis for various applications, such as the identification of individual instances of equipment (for example, network switches ) or the identification of network protocols , as well as for use in various components of computers, including Ethernet MAC addresses or other network interface cards , WWNs for Fiber Channel HBA, and other Fiber Channel and SAS equipment.

Typically, identifiers (both OUIs and derivatives) are represented as a sequence of octets written in pairs of hexadecimal digits separated by characters

- ( hyphen )

used for canonical notation

: ( colon )

used for bit reverse ^[4] (noncanonical) recording

either as a string of the form {FF, FF, ..., FF} or a hexadecimal number.

In some cases, other forms of presentation are used .

Example:
The OUI recorded by the string {AC, DE, 48} can also be represented as follows:

• Hexadecimal number

ACDE48 ₁₆

• Hexadecimal (canonical) format

AC-DE-48

  |  OUI |
 |  Octet 0 |  Octet 1 |  Octet 2 |
 |  AC |  DE |  4 8 |
 | 1010 1100 | 1101 1110 | 0100 1000 |

• Bit-reverse ^[4] (non-canonical) format:

35: 7B: 12

  |  OUI |
 |  Octet 0 |  Octet 1 |  Octet 2 |
 |  3 5 |  7 B |  1 2 |
 | 0011 0101 | 0111 1011 | 0001 0010 |

The assigned identifier has three octets , or 24 bits . But only 22 bits are significant in it. The high-order bit of the first octet of the OUI (in the bit-reverse ^[4] format) is assigned at once in two values ​​- 0 and 1, which are used in MAC addresses to indicate a single or group destination. The bit following it always has value 0 ^[5] . In the canonical format (which is displayed when ipconfig / ifconfig is displayed), the 2 least significant bits in the first octet are significant, respectively. Thus, for all single addresses in canonical format, the second character (the least significant bit of the first octet in binary representation) is always even, for group addresses - odd.

Example: MAC-48 address ACDE48010203 ₁₆

---

Canonical format:

AC-DE-48-01-02-03 (Windows)

AC: DE: 48: 01: 02: 03 (Unix)

ACDE.4801.0203 (Cisco)

  |  MAC 48 |
 |  OUI |  additional identifier |
 |  Octet 0 |  Octet 1 |  Octet 2 |  Octet 3 |  Octet 4 |  Octet 5 |
 |  AC |  DE |  4 8 |  0 1 |  0 2 |  0 3 |
 | 1010 1100 | 1101 1110 | 0100 1000 | 0000 0001 | 0000 0010 | 0000 0011 |
          ||
          ||
          | single (0) or group (1) destination
          |
          always 0 when using OUI

Bit-reverse ^[4] (non-canonical) format:

35: 7B: 12: 80: 40: C0

  |  MAC 48 |
 |  OUI |  additional identifier |
 |  Octet 0 |  Octet 1 |  Octet 2 |  Octet 3 |  Octet 4 |  Octet 5 |
 |  3 5 |  7 B |  1 2 |  8 0 |  4 0 |  C 0 |
 | 0011 0101 | 0111 1011 | 0001 0010 | 1000 0000 | 0100 0000 | 1100 0000 |
  ||
  ||
  | always 0 when using OUI
  |
  single (0) or group (1) destination       

CDI-32 32-bit context-specific identifier

A 32-bit Context Dependent Identifier (CDI-32) is an identifier created by connecting a 24-bit OUI with an 8-bit secondary identifier, which is assigned by the organization that received the OUI.

40-bit context-specific CDI-40 identifier

40-bit Context Dependent Identifier CDI-40 is an identifier created by connecting a 24-bit OUI with a 16-bit secondary identifier, which is assigned by the organization that received the OUI.

MAC-48 48-bit Media Access Control Identifier

48-bit Media Access Control Identifier MAC-48. IEEE considers the term MAC-48 to be obsolete, previously used to refer to a particular case of using the EUI-48 identifier as the hardware address of a network interface (for example, network adapters or other network hardware) for existing network applications based on IEEE 802 standards. In the future, manufacturers and other organizations should use the designation EUI-48. These identifiers are identical when used independently, but there are some features when encapsulating them in EUI-64 .

EUI-48 48-bit Extended Unique Identifier

48-bit Extended Unique Identifier ^[EU] -48 is an identifier created by connecting a 24-bit OUI with a 24-bit additional identifier, which is assigned by the organization that received the OUI.

EUI-60 60-bit Extended Unique Identifier

60-bit Extended Unique Identifier ^{[7] The} EUI-60 is an identifier created by connecting a 24-bit OUI with a 36-bit additional identifier, which is assigned by the organization that received the OUI. In addition to the above options for representing identifiers , a record of the form

  FF-FF-FF: FFFFFFFFF

Previously, this identifier was used as WWN in some data storage systems (Fiber Channel, SAS). Such an application is now considered obsolete by IEEE and EUI-64 should be used instead of EUI-60.

EUI-64 64-bit Extended Unique Identifier

64-bit extended unique identifier ^[8] ( eng. Extended Unique Identifier ) EUI-64 is an identifier created by connecting a 24-bit OUI with a 40-bit additional identifier, which is assigned by the organization that received the OUI.

According to IEEE recommendations, the first 4 digits of an additional (assigned by an organization) identifier should not be FFFE ₁₆ or FFFF ₁₆ (i.e. EUI-64 identifiers of the type ccccccFFFEeeeeee ₁₆ and ccccccFFFFeeeeee _{16 are} not allowed) - they are used to support the encapsulation of MAC-48 and EUI-48 to EUI-64.

Other types

There are other types of identifiers derived from OUIs, but the above list covers the most commonly used ones.

Individual Address Block IAB ^{[3] [9]} is an identifier block created by connecting a 24-bit OUI owned by the IEEE Registration Administration ^[1] with an additional 12-bit identifier assigned to the organization by the Registration Administration IEEE , leaving an extra 12 bits for use by the organization that received the IAB. The resulting 48-bit identifier (IAB) uniquely identifies the organization that received the IAB and provides it with 4,096 unique EUI-48 numbers. The point of assigning an IAB is to allow organizations to get small identifier blocks at a low cost.

Difference between IAB and OUI-36

Both of these identifiers have 36 bits that can be used to generate EUI-48 , but IAB cannot be used to generate EUI-64 . At the time of writing, the registration cost of IAB and EUI-36 is the same.

IAB-based CDI-40

Also possible are IAB - based CDI-40 sequences, which are formed by connecting a 36-bit assigned by IEEE, IAB with a 4-bit additional identifier assigned by the organization that received the IAB.

• GUID
• OID

• Institute of Electrical and Electronics Engineers ( IEEE ). IEEE 802-2001 standard
• Use of the IEEE assigned Organizationally Unique Identifier with ANSI / IEEE Std 802-2001 Local and Metropolitan Area Networks .
• IEEE OUI FAQ
• IEEE OUI and Company ID assignments
• The IEEE Frequently Asked Questions, Registration Authority