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what number is burned on network cards to identify them

Unique identifier assigned to network interfaces for communications on the physical network segment

This commodity is about a type of network address. For the Apple computers, see Macintosh. For other similar terms, run across Mac.

Label of a UMTS router with MAC addresses for LAN and WLAN modules

A media access control address (MAC address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications inside a network segment. This utilise is common in nigh IEEE 802 networking technologies, including Ethernet, Wi-Fi, and Bluetooth. Inside the Open Systems Interconnection (OSI) network model, MAC addresses are used in the medium access command protocol sublayer of the data link layer. Equally typically represented, MAC addresses are recognizable as vi groups of two hexadecimal digits, separated by hyphens, colons, or without a separator.

MAC addresses are primarily assigned by device manufacturers, and are therefore oftentimes referred to equally the burned-in accost, or every bit an Ethernet hardware address, hardware accost, or concrete address. Each address tin be stored in hardware, such as the card's read-only retentivity, or past a firmware machinery. Many network interfaces, nonetheless, back up changing their MAC accost. The address typically includes a manufacturer's organizationally unique identifier (OUI). MAC addresses are formed co-ordinate to the principles of ii numbering spaces based on Extended Unique Identifiers (EUI) managed by the Constitute of Electrical and Electronics Engineers (IEEE): EUI-48, which replaces the obsolete term MAC-48,[1] and EUI-64.[2]

Network nodes with multiple network interfaces, such as routers and multilayer switches, must have a unique MAC accost for each NIC in the same network. However, 2 NICs continued to ii different networks can share the same MAC address.

Address details [edit]

The structure of a 48-scrap MAC address. The b0 scrap distinguishes multicast and unicast addressing and the b1 fleck distinguishes universal and locally administered addressing.

The IEEE 802 MAC address originally comes from the Xerox Network Systems Ethernet addressing scheme.[3] This 48-bit address space contains potentially ii48 (over 281 trillion) possible MAC addresses. The IEEE manages allocation of MAC addresses, originally known as MAC-48 and which it at present refers to as EUI-48 identifiers. The IEEE has a target lifetime of 100 years (until 2080) for applications using EUI-48 space and restricts applications accordingly. The IEEE encourages adoption of the more plentiful EUI-64 for not-Ethernet applications.

The stardom betwixt EUI-48 and MAC-48 identifiers is in name and application but. MAC-48 was used to address hardware interfaces within existing 802-based networking applications; EUI-48 is now used for 802-based networking and is likewise used to identify other devices and software, for example Bluetooth.[2] [four] The IEEE now considers MAC-48 to be an obsolete term.[1] EUI-48 is now used in all cases. In addition, the EUI-64 numbering system originally encompassed both MAC-48 and EUI-48 identifiers by a simple translation mechanism.[2] [a] These translations have since been deprecated.[two]

An Individual Address Block (IAB) is an inactive registry activity which has been replaced by the MA-Due south (MA-S was previously named OUI-36 and have no overlaps in addresses with IAB[v]) registry product equally of January ane, 2014. The IAB uses an OUI from MA-50 (MAC address block large) registry was previously named OUI registry, the term OUI is however in use, simply non for calling a registry[5]) belonging to the IEEE Registration Authority, concatenated with 12 boosted IEEE-provided $.25 (for a total of 36 bits), leaving just 12 bits for the IAB owner to assign to their (up to 4096) private devices. An IAB is ideal for organizations requiring not more than 4096 unique 48-bit numbers (EUI-48). Unlike an OUI, which allows the assignee to assign values in diverse dissimilar number spaces (for example, EUI-48, EUI-64, and the various context-dependent identifier number spaces, like for SNAP or EDID (VSDB field)), the Individual Address Block could just exist used to assign EUI-48 identifiers. All other potential uses based on the OUI from which the IABs are allocated are reserved and remain the holding of the IEEE Registration Authority. Between 2007 and September 2012, the OUI value 00:50:C2 was used for IAB assignments. Afterwards September 2012, the value 40:D8:55 was used. The owners of an already assigned IAB may keep to use the assignment.[6]

MA-South (MAC address cake small) registry activity includes both a 36-bit unique number used in some standards and the assignment of a block of EUI-48 and EUI-64 identifiers (while owner of IAB cannot assign EUI-64) past the IEEE Registration Authority. MA-South does not include assignment of an OUI.

There is too another registry which is chosen MA-G (MAC accost block medium). The MA-K consignment block provides both 2twenty EUI-48 identifiers and 236 EUI-64 identifiers (that means first 28 $.25 are IEEE assigned bits). The first 24 bits of the assigned MA-Yard block are an OUI assigned to IEEE that will not be reassigned, so the MA-Chiliad does non include assignment of an OUI.

Universal vs. local (U/L bit) [edit]

Addresses tin can either be universally administered addresses (UAA) or locally administered addresses (LAA). A universally administered address is uniquely assigned to a device by its manufacturer. The first iii octets (in manual order) identify the organization that issued the identifier and are known as the organizationally unique identifier (OUI).[2] The remainder of the accost (three octets for EUI-48 or five for EUI-64) are assigned by that organization in almost whatsoever manner they please, subject to the constraint of uniqueness. A locally administered address is assigned to a device by software or a network ambassador, overriding the burned-in address for physical devices.

Locally administered addresses are distinguished from universally administered addresses by setting (assigning the value of i to) the second-least-significant bit of the offset octet of the accost. This bit is also referred to as the U/50 bit, brusk for Universal/Local, which identifies how the address is administered.[7] [8] If the bit is 0, the address is universally administered, which is why this bit is 0 in all UAAs. If it is 1, the address is locally administered. In the example address 06-00-00-00-00-00 the first octet is 06 (hexadecimal), the binary grade of which is 000001ane0, where the second-to the lowest degree-meaning scrap is 1. Therefore, information technology is a locally administered address.[9] Fifty-fifty though many hypervisors manage dynamic MAC addresses within their own OUI, oft it is useful to create an entire unique MAC within the LAA range.[10]

Universal addresses that are administered locally [edit]

In virtualisation, hypervisors such equally QEMU and Xen take their ain OUIs. Each new virtual auto is started with a MAC address prepare by assigning the terminal three bytes to be unique on the local network. While this is local administration of MAC addresses, it is not an LAA in the IEEE sense.

An historical instance of this hybrid situation is the DECnet protocol, where the universal MAC address (OUI AA-00-04, Digital Equipment Corporation) is administered locally. The DECnet software assigns the last 3 bytes for the consummate MAC address to exist AA-00-04-00-Twenty-YY where Twenty-YY reflects the DECnet network accost xx.yy of the host. This eliminates the demand for DECnet to have an accost resolution protocol since the MAC accost for any DECnet host can be adamant from its DECnet address.

Unicast vs. multicast (I/Yard chip) [edit]

The least meaning bit of an address'due south beginning octet is referred to as the I/G, or Individual/Grouping, chip.[7] [8] When this bit is 0 (zero), the frame is meant to accomplish simply 1 receiving NIC.[11] This type of transmission is called unicast. A unicast frame is transmitted to all nodes inside the standoff domain. In a mod wired setting the collision domain commonly is the length of the Ethernet cable between 2 network cards. In a wireless setting, the standoff domain is all receivers that can detect a given wireless point. If a switch does not know which port leads to a given MAC accost, the switch volition forward a unicast frame to all of its ports (except the originating port), an activeness known as unicast overflowing.[12] Only the node with the matching hardware MAC address will accept the frame; network frames with non-matching MAC-addresses are ignored, unless the device is in promiscuous manner.

If the to the lowest degree significant bit of the kickoff octet is set up to 1 (i.e. the second hexadecimal digit is odd) the frame will yet be sent only once; still, NICs will cull to accept it based on criteria other than the matching of a MAC accost: for instance, based on a configurable list of accepted multicast MAC addresses. This is chosen multicast addressing.

The IEEE has built in several special address types to allow more than one network interface card to be addressed at one fourth dimension:

  • Packets sent to the circulate address, all one bits, are received by all stations on a local area network. In hexadecimal the broadcast accost would exist FF:FF:FF:FF:FF:FF . A broadcast frame is flooded and is forwarded to and accepted by all other nodes.
  • Packets sent to a multicast accost are received by all stations on a LAN that have been configured to receive packets sent to that address.
  • Functional addresses identify one or more Token Ring NICs that provide a detail service, defined in IEEE 802.five.

These are all examples of group addresses, every bit opposed to individual addresses; the least significant chip of the start octet of a MAC address distinguishes individual addresses from group addresses. That fleck is set to 0 in private addresses and ready to 1 in group addresses. Group addresses, like individual addresses, can exist universally administered or locally administered.

Ranges of group and locally administered addresses [edit]

The U/L and I/1000 bits are handled independently, and there are instances of all four possibilities.[nine] IPv6 multicast uses locally administered, multicast MAC addresses in the range 33‑33‑twenty‑xx‑xx‑twenty (with both bits set up).[13]

Given the locations of the U/L and I/One thousand bits, they tin be discerned in a single digit in common MAC address notation equally shown in the following table:

Universal/Local and Individual/Grouping bits in MAC addresses

U/50

I/M

 Universally administered Locally administered
Unicast (private) x0‑20‑xx‑xx‑xx‑xx
x4‑20‑xx‑xx‑twenty‑xx
x8‑xx‑twenty‑xx‑xx‑xx
10C‑xx‑xx‑xx‑twenty‑xx 		xtwo‑twenty‑xx‑20‑20‑xx
x6‑xx‑twenty‑20‑xx‑20
xA‑xx‑twenty‑xx‑xx‑xx
tenE‑xx‑xx‑20‑20‑xx
Multicast (group) xi‑xx‑xx‑twenty‑twenty‑xx
ten5‑xx‑20‑xx‑xx‑xx
ten9‑20‑xx‑twenty‑xx‑xx
10D‑20‑xx‑xx‑twenty‑xx 		xthree‑xx‑xx‑xx‑xx‑xx
107‑xx‑20‑xx‑xx‑20
xB‑xx‑twenty‑xx‑xx‑xx
xF‑xx‑20‑20‑xx‑xx

Applications [edit]

The following network technologies use the EUI-48 identifier format:

  • IEEE 802 networks
    • Ethernet
    • 802.xi wireless networks (Wi-Fi)
    • Bluetooth
    • IEEE 802.5 Token Ring
  • Cobweb Distributed Data Interface (FDDI)
  • Asynchronous Transfer Way (ATM), switched virtual connections merely, as part of an NSAP address
  • Fibre Channel and Serial Fastened SCSI (every bit part of a World Wide Proper noun)
  • The ITU-T One thousand.hn standard, which provides a manner to create a high-speed (up to one gigabit/south) local area network using existing home wiring (power lines, phone lines and coaxial cables). The G.hn Awarding Protocol Convergence (APC) layer accepts Ethernet frames that utilise the EUI-48 format and encapsulates them into G.hn Medium Access Control Service Data Units (MSDUs).

Every device that connects to an IEEE 802 network (such as Ethernet and Wi-Fi) has an EUI-48 address. Common networked consumer devices such as PCs, smartphones and tablet computers use EUI-48 addresses.

EUI-64 identifiers are used in:

  • IEEE 1394 (FireWire)
  • InfiniBand
  • IPv6 (Modified EUI-64 as the least-pregnant 64 bits of a unicast network address or link-local address when stateless address autoconfiguration is used.)[fourteen] IPv6 uses a modified EUI-64, treats MAC-48 every bit EUI-48 instead (as it is chosen from the aforementioned address puddle) and inverts the local bit.[b] This results in extending MAC addresses (such equally IEEE 802 MAC accost) to modified EUI-64 using only FF-Iron (and never FF-FF ) and with the local bit inverted.[15]
  • ZigBee / 802.xv.four / 6LoWPAN wireless personal-area networks
  • IEEE 11073-20601 (IEEE 11073-20601 compliant medical devices)[sixteen]

Usage in hosts [edit]

On circulate networks, such equally Ethernet, the MAC address is expected to uniquely identify each node on that segment and allows frames to exist marked for specific hosts. It thus forms the basis of most of the link layer (OSI Layer 2) networking upon which upper-layer protocols rely to produce complex, functioning networks.

Many network interfaces support changing their MAC accost. On near Unix-like systems, the control utility ifconfig may be used to remove and add link address aliases. For instance, the agile ifconfig directive may be used on NetBSD to specify which of the fastened addresses to activate.[17] Hence, various configuration scripts and utilities allow the randomization of the MAC accost at the time of booting or before establishing a network connexion.

Changing MAC addresses is necessary in network virtualization. In MAC spoofing, this is practiced in exploiting security vulnerabilities of a computer system. Some modern operating systems, such as Apple tree iOS and Android, especially in mobile devices, are designed to randomize the assignment of a MAC address to network interface when scanning for wireless admission points to avert tracking systems.[xviii] [nineteen]

In Cyberspace Protocol (IP) networks, the MAC address of an interface corresponding to an IP address may be queried with the Address Resolution Protocol (ARP) for IPv4 and the Neighbor Discovery Protocol (NDP) for IPv6, relating OSI Layer 3 addresses to Layer 2 addresses.

Tracking [edit]

Randomization [edit]

Co-ordinate to Edward Snowden, the US National Security Agency has a system that tracks the movements of mobile devices in a metropolis by monitoring MAC addresses.[20] To avert this exercise, Apple has started using random MAC addresses in iOS devices while scanning for networks.[eighteen] Other vendors followed rapidly. MAC address randomization during scanning was added in Android starting from version 6.0,[19] Windows 10,[21] and Linux kernel iii.eighteen.[22] The actual implementations of the MAC address randomization technique vary largely in different devices.[23] Moreover, various flaws and shortcomings in these implementations may let an attacker to track a device fifty-fifty if its MAC address is changed, for instance its probe requests' other elements,[24] [25] or their timing.[26] [23] If random MAC addresses are not used, researchers have confirmed that it is possible to link a real identity to a particular wireless MAC address.[27] [28]

Other data leakage [edit]

Using wireless access points in SSID-hidden mode (network cloaking), a mobile wireless device may not only disclose its ain MAC accost when traveling, but fifty-fifty the MAC addresses associated to SSIDs the device has already connected to, if they are configured to transport these as function of probe request packets. Culling modes to forbid this include configuring access points to be either in beacon-broadcasting way or probe-response with SSID fashion. In these modes, probe requests may be unnecessary or sent in broadcast mode without disclosing the identity of previously known networks.[29]

Anonymization [edit]

Notational conventions [edit]

The standard (IEEE 802) format for printing EUI-48 addresses in man-friendly form is six groups of two hexadecimal digits, separated by hyphens ( - ) in manual order (eastward.m. 01-23-45-67-89-AB ). This grade is also commonly used for EUI-64 (e.g. 01-23-45-67-89-AB-CD-EF ).[2] Other conventions include half dozen groups of ii hexadecimal digits separated past colons (:) (e.thou. 01:23:45:67:89:AB ), and 3 groups of iv hexadecimal digits separated by dots (.) (e.g. 0123.4567.89AB ); again in manual guild.[30]

Chip-reversed notation [edit]

The standard notation, too called approved format, for MAC addresses is written in transmission order with the least significant bit of each byte transmitted first, and is used in the output of the ifconfig, ip address, and ipconfig commands, for case.

However, since IEEE 802.iii (Ethernet) and IEEE 802.iv (Token Double-decker) send the bytes (octets) over the wire, left-to-right, with the to the lowest degree significant bit in each byte beginning, while IEEE 802.five (Token Band) and IEEE 802.6 (FDDI) transport the bytes over the wire with the almost significant bit offset, confusion may arise when an accost in the latter scenario is represented with bits reversed from the canonical representation. For example, an address in canonical form 12-34-56-78-9A-BC would be transmitted over the wire as $.25 01001000 00101100 01101010 00011110 01011001 00111101 in the standard transmission guild (least significant bit first). Just for Token Ring networks, it would be transmitted equally bits 00010010 00110100 01010110 01111000 10011010 10111100 in most-pregnant-bit first club. The latter might exist incorrectly displayed as 48-2C-6A-1E-59-3D . This is referred to as flake-reversed order, not-canonical course, MSB format, IBM format, or Token Band format, as explained in RFC 2469.

See also [edit]

  • Hot Standby Router Protocol
  • MAC filtering
  • Network management
  • Sleep Proxy Service, which may spoof another device'southward MAC accost during certain periods
  • Transparent bridging
  • Virtual Router Back-up Protocol

Notes [edit]

  1. ^ To catechumen a MAC-48 into an EUI-64, copy the OUI, suspend the 2 octets FF-FF and so re-create the organization-specified extension identifier. To convert an EUI-48 into an EUI-64, the same process is used, but the sequence inserted is FF-Atomic number 26 .[two] In both cases, the process could be trivially reversed when necessary. Organizations issuing EUI-64s were cautioned confronting issuing identifiers that could be confused with these forms.
  2. ^ With local identifiers indicated with a zero bit, locally assigned EUI-64 begin with leading zeroes and information technology is easier for administrators to type locally assigned IPv6 addresses based on the modified EUI-64

References [edit]

  1. ^ a b "MAC Accost Block Small (MA-S)". Retrieved 2019-02-24 .
  2. ^ a b c d due east f chiliad "Guidelines for Employ of Extended Unique Identifier (EUI), Organizationally Unique Identifier (OUI), and Visitor ID (CID)" (PDF). IEEE Standards Association. IEEE. Retrieved 5 Baronial 2018.
  3. ^ IEEE Std 802-2001 (PDF). The Plant of Electrical and Electronics Engineers, Inc. (IEEE). 2002-02-07. p. nineteen. ISBN978-0-7381-2941-9 . Retrieved 2011-09-08 . The universal administration of LAN MAC addresses began with the Xerox Corporation administering Block Identifiers (Block IDs) for Ethernet addresses.
  4. ^ "IEEE-SA - IEEE Registration Dominance". standards.ieee.org . Retrieved 2018-09-20 .
  5. ^ a b "IEEE-SA - IEEE Registration Authorization". standards.ieee.org . Retrieved 2018-11-27 .
  6. ^ "IEEE-SA - IEEE Registration Authority". standards.ieee.org . Retrieved 2018-09-20 .
  7. ^ a b "Ethernet frame IG/LG bit explanation - Wireshark". networkengineering.stackexchange.com . Retrieved 2021-01-05 .
  8. ^ a b "RFC 4291 IP Version 6 Addressing Architecture Appendix A". tools.ietf.org . Retrieved 2021-01-05 .
  9. ^ a b "Standard Group MAC Addresses: A Tutorial Guide" (PDF). IEEE-SA. Retrieved 2018-09-twenty .
  10. ^ "Generating a New Unique MAC Address". RedHat. Retrieved 2020-06-xv .
  11. ^ "Guidelines for Fibre Channel Use of the Organizationally Unique Identifier (OUI)" (PDF). IEEE-SA. Retrieved 2018-10-eleven .
  12. ^ "Overview of Layer 2 Switched Networks and Communication | Getting Started with LANs | Cisco Back up Community | 5896 | 68421". supportforums.cisco.com. 2011-07-23. Retrieved 2016-05-17 .
  13. ^ RFC 7042 2.3.i.
  14. ^ Southward. Thomson; T. Narten; T. Jinmei (September 2007). IPv6 Stateless Accost Autoconfiguration. Network Working Group, IETF. doi:10.17487/RFC4862. RFC 4862.
  15. ^ IANA Considerations and IETF Protocol Usage for IEEE 802 Parameters. IETF. September 2008. sec. 2.2.i. doi:10.17487/RFC7042. RFC 7042.
  16. ^ IEEE P11073-20601 Health informatics—Personal health device advice Function 20601: Application contour—Optimized Substitution Protocol
  17. ^ "ifconfig(eight) manual page". Retrieved 16 October 2016.
  18. ^ a b Mamiit, Aaron (2014-06-12). "Apple Implements Random MAC Address on iOS 8. Farewell, Marketers". Tech Times . Retrieved 2014-12-01 .
  19. ^ a b "Android vi.0 Changes". Android developers . Retrieved 2018-08-22 .
  20. ^ Bamford, James (2014-08-thirteen). "The Nigh Wanted Human in the Earth". Wired: 4. Retrieved 2014-12-01 .
  21. ^ Winkey Wang. "Wireless networking in Windows 10".
  22. ^ Emmanuel Grumbach. "iwlwifi: mvm: support random MAC accost for scanning". Linux commit effd05ac479b . Retrieved 2018-08-22 .
  23. ^ a b Célestin Matte (Dec 2017). Wi-Fi Tracking: Fingerprinting Attacks and Counter-Measures. 2017 (Theses). Université de Lyon. Retrieved 2018-08-22 .
  24. ^ Vanhoef Mathy and Matte Célestin and Cunche Mathieu and Cardoso Leonardo and Piessens Frank (2016-05-30). "Why MAC address randomization is not plenty: An analysis of Wi-Fi network discovery mechanisms". Retrieved 2018-08-22 .
  25. ^ Martin Jeremy and Mayberry Travis and Donahue Collin and Foppe Lucas and Chocolate-brown Lamont and Riggins Chadwick and Rye Erik C and Brown Dane. "A written report of MAC address randomization in mobile devices and when it fails" (PDF). 2017 . Retrieved 2018-08-22 .
  26. ^ Matte Célestin and Cunche Mathieu and Rousseau Franck and Vanhoef Mathy (2016-07-eighteen). "Defeating MAC accost randomization through timing attacks". Retrieved 2018-08-22 .
  27. ^ Cunche, Mathieu. "I know your MAC Accost: Targeted tracking of individual using Wi-Fi" (PDF). 2013 . Retrieved nineteen Dec 2014.
  28. ^ Muhammad Hassan. "How to Find iPhone MAC Address".
  29. ^ "Hidden network no beacons". security.stackexchange.com . Retrieved 16 October 2016.
  30. ^ "Agentless Host Configuration Scenario". Configuration Guide for Cisco Secure ACS 4.2. Cisco. February 2008. Archived from the original on 2016-08-02. Retrieved 2015-09-19 . You tin can enter the MAC accost in the post-obit formats for representing MAC-48 addresses in human-readable form: half dozen groups of two hexadecimal digits, separated by hyphens (-) in transmission order,[...]6 groups of two separated by colons (:),[...]three groups of four hexadecimal digits separated by dots (.)...

External links [edit]

  • IEEE Registration Authority Tutorials
  • IEEE Registration Dominance - Ofttimes Asked Questions
  • IEEE Public OUI and Company ID, etc. Assignment lookup
  • IEEE Public OUI/MA-L list
  • IEEE Public OUI-28/MA-One thousand list
  • IEEE Public OUI-36/MA-Southward listing
  • IEEE Public IAB list
  • IEEE IAB and OUI MAC Address Lookup Database and API
  • RFC 7042. IANA Considerations and IETF Protocol and Documentation Usage for IEEE 802 Parameters
  • IANA list of Ethernet Numbers
  • Wireshark's OUI Lookup Tool and MAC accost list

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Source: https://en.wikipedia.org/wiki/MAC_address