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Encyclopedia > MAC address

In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). It is a number that acts like a name for a particular network adapter, so, for example, the network cards (or built-in network adapters) in two different computers will have different names, or MAC addresses, as would an Ethernet adapter and a wireless adapter in the same computer, and as would multiple network cards in a router. However, it is possible to change the MAC address on most of today's hardware, often referred to as MAC spoofing. Computer networks may be classified according to the network layer at which they operate according to some basic reference models that are considered to be standards in the industry such as the seven layer OSI reference model and the four layer Internet Protocol Suite model. ... The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ... This page is a candidate for speedy deletion. ... A transitional network card with both BNC Thinnet (left) and Twisted pair (right) connectors. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ...


Most layer 2 network protocols use one of three numbering spaces managed by the IEEE: MAC-48, EUI-48, and EUI-64, which are designed to be globally unique. Not all communications protocols use MAC addresses, and not all protocols require globally unique identifiers. The IEEE claims trademarks on the names "EUI-48" and "EUI-64". (The "EUI" stands for Extended Unique Identifier .) The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. ... In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... “(TM)” redirects here. ...


MAC addresses, unlike IP addresses and IPX addresses, are not divided into "host" and "network" portions. Therefore, a host cannot determine from the MAC address of another host whether that host is on the same layer 2 network segment as the sending host or a network segment bridged to that network segment. This article or section does not cite any references or sources. ... See also Ericsson IPX Internetwork Packet Exchange (IPX) is the OSI-model Network layer protocol in the IPX/SPX protocol stack. ... A network segment is a portion of a computer network wherein every device communicates using the same physical layer. ... A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. ...


ARP is commonly used to convert from addresses in a layer 3 protocol such as Internet Protocol (IP) to the layer 2 MAC address. On broadcast networks, such as Ethernet, the MAC address allows each host to be uniquely identified and allows frames to be marked for specific hosts. It thus forms the basis of most of the layer 2 networking upon which higher OSI Layer protocols are built to produce complex, functioning networks. In computer networking, the Address Resolution Protocol (ARP) is the standard method for finding a hosts hardware address when only its network layer address is known. ... The network layer is level three of the seven level OSI model. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. ... The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative. ...

Contents

Address details

The original IEEE 802 MAC address, comes from the original Xerox Ethernet addressing scheme.[1] This 48-bit address space contains potentially 248 or 281,474,976,710,656 possible MAC addresses. Image File history File links No higher resolution available. ... IEEE 802 refers to a family of IEEE standards about local area networks and metropolitan area networks. ... Xerox Corporation (NYSE: XRX) (name pronounced ) is a global document management company, which manufactures and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies. ...


All three numbering systems use the same format and differ only in the length of the identifier. Addresses can either be "universally administered addresses" or "locally administered addresses."


A universally administered address is uniquely assigned to a device by its manufacturer; these are sometimes called "burned-in addresses." The first three octets (in transmission order) identify the organization that issued the identifier and are known as the Organizationally Unique Identifier (OUI). The following three (MAC-48 and EUI-48) or five (EUI-64) octets are assigned by that organization in nearly any manner they please, subject to the constraint of uniqueness. The IEEE expects the MAC-48 space to be exhausted no sooner than the year 2100; EUI-64s are not expected to run out in the foreseeable future. In computer technology and networking, an octet is a group of 8 bits. ... Organizationally Unique Identifier (or OUI) is a term referring to a 24-bit number assigned to a company or organization for use in various computer hardware products, including ethernet Network Interface Cards and Fibre Channel Host Bus Adapters. ... 2100 can refer to either: The first year of the 2100s decade. ...


A locally administered address is assigned to a device by a network administrator, overriding the burned-in address. Locally administered addresses do not contain OUIs.


Universally administered and locally administered addresses are distinguished by setting the second least significant bit of the most significant byte of the address. If the bit is 0, the address is universally administered. If it is 1, the address is locally administered. The bit is 0 in all OUIs. For example, 02-00-00-00-00-01. The most significant byte is 02h. The binary is 00000010 and the second least significant bit is 1. Therefore, it is a locally administered address.[2] The binary representation of decimal 149, with the lsb highlighted. ...


If the least significant bit of the most significant byte is set to a 0, the packet is meant to reach only one receiving NIC. This is called unicast. If the least significant bit of the most significant byte is set to a 1, the packet is meant to be sent only once but still reach several NICs. This is called multicast. A network card, network adapter or NIC (network interface controller) is a piece of computer hardware designed to allow computers to communicate over a computer network. ... In computer networks, unicast is the sending of information packets to a single destination. ... Routing Schemes anycast broadcast multicast unicast Multicast is sometimes also used to refer to a multiplexed broadcast, although that is a very different thing and should not be confused. ...


MAC-48 and EUI-48 addresses are usually shown in hexadecimal format, with each octet separated by a dash or colon. An example of a MAC-48 address would be "00-08-74-4C-7F-1D". If you cross-reference the first three octets with IEEE's OUI assignments,[3] you can see that this MAC address came from Dell Computer Corp. The last three octets represent the serial number assigned to the adapter by the manufacturer. In mathematics and computer science, hexadecimal, base-16, or simply hex, is a numeral system with a radix, or base, of 16, usually written using the symbols 0–9 and A–F, or a–f. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... Dell, Inc. ...


The following technologies use the MAC-48 identifier format:

The distinction between EUI-48 and MAC-48 identifiers is purely semantic: MAC-48 is used for network hardware; EUI-48 is used to identify other devices and software. (Thus, by definition, an EUI-48 is not in fact a "MAC address", although it is syntactically indistinguishable from one and assigned from the same numbering space.) Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... IEEE 802. ... Bluetooth logo This article is about the electronic protocol named after Harald Bluetooth Gormson. ... Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ... A Network Service Access Point (NSAP) addresses, defined in ISO/IEC 8348, are identifying labels for network endpoints used in OSI networking. ... Fibre Channel is a gigabit-speed network technology primarily used for storage networking. ... 2. ... A World Wide Name (WWN) or World Wide Identifier (WWID) is a unique identifier in a Fibre Channel or Serial Attached SCSI storage network. ...


Note: 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 within existing 802-based networking applications and should not be used in the future. Instead, the term EUI-48 should be used for this purpose.


EUI-64 identifiers are used in:

  • FireWire
  • IPv6 (as the low-order 64 bits of a unicast network address when temporary addresses are not being used)
  • ZigBee / 802.15.4 wireless personal-area networks

The IEEE has built in several special address types to allow more than one Network Interface Card to be addressed at one time: The 6-pin and 4-pin FireWire Connectors The alternative ethernet-style cabling used by 1394c FireWire is Apple Inc. ... Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... IEEE 802. ... A transitional network card with both BNC Thinnet (left) and Twisted pair (right) connectors. ...

  • Packets sent to the broadcast address, all one bits, are received by all stations on a local area network. In hexadecimal the broadcast address would be "FF:FF:FF:FF:FF:FF".
  • Packets sent to a multicast address are received by all stations on a LAN that have been configured to receive packets sent to that address.
  • Functional addresses identify one of more Token Ring NICs that provide a particular service, defined in IEEE 802.5.

These are "group addresses", as opposed to "individual addresses"; the least significant bit of the first octet of a MAC address distinguishes individual addresses from group addresses. That bit is set to 0 in individual addresses and 1 in group addresses. Group addresses, like individual addresses, can be universally administered or locally administered. In computer networking, a broadcast address is an IP address that allows information to be sent to all machines on a given subnet rather than a specific machine. ... “LAN” redirects here. ... In mathematics and computer science, hexadecimal, base-16, or simply hex, is a numeral system with a radix, or base, of 16, usually written using the symbols 0–9 and A–F, or a–f. ... In computer networking a multicast address is an identifier for a group of hosts that have joined a multicast group. ... IBM token ring refers to IBMs implementation of token ring technology for linking personal computers in a local area network (LAN). ...


In addition, the EUI-64 numbering system encompasses both MAC-48 and EUI-48 identifiers by a simple translation mechanism. To convert a MAC-48 into an EUI-64, copy the OUI, append the two octets "FF-FF", and then copy the organization-specified part. To convert an EUI-48 into an EUI-64, the same process is used, but the sequence inserted is "FF-FE". In both cases, the process can be trivially reversed when necessary. Organizations issuing EUI-64s are cautioned against issuing identifiers that could be confused with these forms. The IEEE policy is to discourage new uses of 48-bit identifiers in favor of the EUI-64 system.


IPv6—one of the most prominent standards that uses EUI-64—applies these rules inconsistently. Due to an error in the appendix to the specification of IPv6 addressing, it is standard practice to extend MAC-48 addresses (such as IEEE 802 MAC address) to EUI-64 using "FF-FE" rather than "FF-FF." Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. ...


Individual address block

An Individual Address Block comprises a 24-bit OUI managed by the IEEE Registration Authority, followed by 12 IEEE-provided bits (identifying the organization), and 12 bits for the owner to assign to individual devices. An IAB is ideal for organizations requiring fewer than 4097 unique 48-bit numbers (EUI-48).[4] The Individual Address Block (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... Organizationally Unique Identifier (or OUI) is a term referring to a 24-bit number assigned to a company or organization for use in various computer hardware products, including ethernet Network Interface Cards and Fibre Channel Host Bus Adapters. ...


Printed format

The standard (IEEE 802) format for printing MAC-48 addresses in human-readable media is six groups of two hexadecimal digits, separated by hyphens (-) in transmission order, e.g. 01-23-45-67-89-ab. This form is also commonly used for EUI-64. Other conventions include six groups of two separated by colons (:), e.g. 01:23:45:67:89:ab; or three groups of four hexadecimal digits separated by dots (.), e.g. 0123.4567.89ab; again in transmission order. In mathematics and computer science, hexadecimal, base-16, or simply hex, is a numeral system with a radix, or base, of 16, usually written using the symbols 0–9 and A–F, or a–f. ...


See also

A Network Service Access Point (NSAP) addresses, defined in ISO/IEC 8348, are identifying labels for network endpoints used in OSI networking. ... Cisco Systems, Inc. ... Hot Standby Router Protocol (HSRP) is a Cisco proprietary redundancy protocol for establishing a fault-tolerant default gateway, and has been described in detail in RFC 2281. ... Virtual Router Redundancy Protocol (VRRP) is a non-proprietary redundancy protocol described in RFC 3768 designed to increase the availability of the default gateway servicing hosts on the same subnet. ... This article or section does not cite any references or sources. ... OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. ... The Common Adress Redundancy Protocol or CARP is a protocol which allows multiple hosts on the same local network to share a set of IP addresses. ...

References

  1. ^ IEEE Std 802®-2001
  2. ^ Standard Group MAC Addresses: A Tutorial Guide
  3. ^ IEEE OUI and Company_id Assignments
  4. ^ What is an Individual Address Block?. Retrieved on 2006-07-09.

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 190th day of the year (191st in leap years) in the Gregorian calendar. ...

External links


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