IEEE 802C-2017 pdf free.IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture Amendment 2: Local Medium Access Control (MAC) Address Usage.
The U/L bit of a local MAC address is set to 1, indicating that the remaining bits (i.e., all bits except the U/L bit and the J/G bit, which is set as described in 8.2.2) are locally administered. Local MAC addresses are not presumed globally unique across all IEEE 802 networks. The locally administered bits of local MAC addresses arc arbitrarily assignable under the condition that local MAC addresses arc unique within a LAN (which may be a bridged LAN or virtual bridged LAN). In a virtual bridged LAN wherein the bridges use Independent VLAN Learning, the uniqueness condition applies to each VLAN rather than to the entire virtual bridged LAN. Any failure of such uniqueness invalidates the fundamental premises of IEEE 802 network operation and may lead to disruption. Therefore, administrators should ensure that the probability of local MAC address non-uniqueness is acceptably small.
While a local administrator may assign addresses throughout the local range, the optional Structured Local Address Plan (SLAP) specifics different assignment approaches in Ibur specified regions of local MAC address space.
Unlike universal addresses, which arc persistent to the MAC entity, local MAC addresses arc not necessarily persistent. The local MAC address assigned to a MAC entity, including any subsequent change to that assignment, is entirely within the scope oithe local administration.
8.4.2 Local MAC address assignment protocols
An address assignment protocol assigning local MAC addresses to devices on a LAN should ensure uniqueness of those addresses, per the description of F. 1.2 of IEEE Std 802. IQ. That standard’s Annex F also identities risks of non-uniqueness.
When multiple address assignment protocols operate on a LAN without centralized administration, address duplication is possible even if each protocol alone is designed to avoid duplication. When multiple address assignment protocols operate on a LAN without centralized administration, address duplication is possible, even if each protocol alone is designed to avoid duplication, unless such protocols assign addresses from disjoint address pools.
The subelauses below specify the usage of local MAC address space according to the SLAP. Administrators who deploy multiple protocols on a LAN in accordance with the SLAP will enable the unique assignment of local MAC addresses within the LAN as long as each protocol maintains unique assignments within its own address subspace.
8.4.3 Structured Local Address Plan (SLAP)
The SLAP specifies use of local MAC address space. Under the SLAP, the use is specified differently in four quadrants of local MAC address space.
The least and second least significant bits of the initial octet of a MAC address are designated the M bit and X bit, respectively, using the terminology specified in the IEEE RA“Guidelines for Use Organizationally Unique Identifier (OUI) and Company ID (CID)” [Ba]. The third and fourth least significant bits of the initial octet in the local MAC address are designated the Y bit and Z bit, respectively, as illustrated for a 48-bit address in Figure 11a(see NOTE 4 of 8.2.2).IEEE 802C pdf download.