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For questions about Media Access Control (MAC) address which is used as the OSI layer-2 address for many OSI layer-2 protocols.

A Media Access Control (MAC) address is used by many OSI layer-2 protocols as the OSI layer-2 address used in the frame encapsulation. There are two types of MAC address:

EUI-48:

A 48-bit MAC address comprised of two parts: a 24-bit Organizationally Unique Identifier (OUI), and a 24-bit number unique within the OUI.

48-bit MAC addresses are the most commonly used type of MAC address, and they are used for protocols such as ethernet, token ring, FDDI, 802.11 Wi-FI, etc.

EUI-64:

A 64-bit MAC address can have one of three different formats:

  • MA-L assignment: a 24-bit Organizationally Unique Identifier (OUI), and a 40-bit number unique within the OUI.
  • MA-M: a 28-bit Organizationally Unique Identifier (OUI), and a 36-bit number unique within the OUI.
  • MA-S: a 36-bit Organizationally Unique Identifier (OUI), and a 28-bit number unique within the OUI.

64-bit MAC addresses are used primarily by wireless personal area network (WPAN) protocols.

IPv6 SLAAC uses a modified EUI-64 address to create an OSI layer-3 address from either a 48-bit or 64-bit MAC address.

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