An Extended Local Identifier (ELI) is created by concatenation from a CID, which comprises the initial three (most significant) octets. The ELI-48 is a 48- bit ELI and the ELI-64 is a 64-bit ELI. Since CID assignments made by the IEEE RA have the X bit equal to 1, an ELI created as an extended identifier from an assigned CID has U/L=1 and is thus,when used as a MAC address, a local address. Local addresses are not globally unique, and a network administrator is responsible for assuring that any local addresses assigned are unique within the span of use. (Uniqueness of local addresses typically does not need to extend beyond a router.) IEEE Std 802 (beginning with the amendment IEEE Std 802c-2017) specifies the Structured Local Address Plan (SLAP), which describes the use of ELIs in one quadrant of local MAC address space, based on the specified values of the CID Y bit and Z bit. In other quadrants of local MAC address space, the SLAP describes the use of Standard Assigned Identifiers (SAIs) and Administratively Assigned Identifiers (AAIs) not based on a CID. Since all CID assignments made by the IEEE RA have the M bit equal to 0, an ELI created as an extended identifier from an assigned CID has I/G=0 and is thus, when used as a MAC address, an individual address. The assignee of a CID may assign local group MAC addresses by extending a modified version of the assigned CID by setting the M bit to 1 (so that I/G=1). The resulting extended identifier is an ELI.
An Extended Local Identifier (ELI) is created by concatenation from a CID, which comprises the initial three (most significant) octets. The ELI-48 is a 48- bit ELI and the ELI-64 is a 64-bit ELI. <br>Since CID assignments made by the IEEE RA have the X bit equal to 1, an ELI created as an extended identifier from an assigned CID has U/L=1 and is thus,when used as a MAC address, a local address. Local addresses are not globally unique, and a network administrator is responsible for assuring that any local addresses assigned are unique within the span of use. (Uniqueness of local addresses typically does not need to extend beyond a router.) IEEE Std 802 (beginning with the amendment IEEE Std 802c-2017) specifies the Structured Local Address Plan (SLAP), which describes the use of ELIs in one quadrant of local MAC address space, based on the specified values of the CID Y bit and Z bit. In other quadrants of local MAC address space, the SLAP describes the use of Standard Assigned Identifiers (SAIs) and Administratively Assigned Identifiers (AAIs) not based on a CID. Since all CID assignments made by the IEEE RA have the M bit equal to 0, an ELI created as an extended identifier from an assigned CID has I/G=0 and is thus, when used as a MAC address, an individual address. The assignee of a CID may assign local group MAC addresses by extending a modified version of the assigned CID by setting the M bit to 1 (so that I/G=1). The resulting extended identifier is an ELI.
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