Label of a router with MAC addresses for and modules A media access control address ( MAC address) of a device is a assigned to a (NIC) for communications at the of a network segment. MAC addresses are used as a for most network technologies, including,. In this context, MAC addresses are used in the protocol sublayer. A MAC may be referred to as the burned-in address ( BIA). It may also be known as an Ethernet hardware address ( EHA), hardware address or physical address (not to be confused with a ). A may have multiple NICs and each NIC must have a unique MAC address. Sophisticated such as a or may require one or more permanently assigned MAC addresses. MAC addresses are most often assigned by the manufacturer of a NIC and are stored in its hardware, such as the card's or some other mechanism. A MAC address may include the manufacturer's (OUI). MAC addresses are formed according to the rules of one of three numbering name spaces managed by the (IEEE): EUI-48 (it replaces the obsolete term MAC-48) and EUI-64. EUI is an abbreviation for Extended Unique Identifier. Diagram showing the structure of a MAC-48 network address, explicitly showing the positions of the / bit and the OUI/local address type bit. The original MAC address comes from the original Ethernet addressing scheme. This address space contains potentially 2 48 or 281,474,976,710,656 possible MAC addresses. The manages allocation of MAC addresses, originally known as MAC-48 and which it now 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 non-Ethernet applications. The distinction between EUI-48 and MAC-48 identifiers is purely nominal: MAC-48 was used to address hardware interfaces within existing 802-based networking applications; EUI-48 is also used to identify other devices and software, for example. Select your network connection, and then click “Advanced.” You’ll find IP address information on the “TCP/IP” tab and the MAC address on the “Hardware” tab. IPhone and iPad. To find this information on an iPhone, iPad, or iPod Touch running Apple’s iOS, first head to Settings > Wi-Fi. The IEEE now considers the label MAC-48 to be an obsolete term. EUI-48 should be used for this purpose. In addition, the EUI-64 numbering system encompasses both MAC-48 and EUI-48 identifiers by a simple translation mechanism, but now it is deprecated. To convert a MAC-48 into an EUI-64, copy the (OUI), append the two FF-FF (though now as MAC-48 is deprecated, FF-FF will never be used) and then copy 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-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. — one of the most prominent standards that uses a Modified EUI-64 — treats MAC-48 as EUI-48 instead (as it is chosen from the same address pool) and toggles the U/L bit (as this makes it easier to type locally assigned IPv6 addresses based on the Modified EUI-64). This results in extending MAC addresses (such as IEEE 802 MAC address) to Modified EUI-64 using only FF-FE (and never FF-FF) and with the U/L bit inverted.
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March 2019
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