This read-write object selects the MAC type the local BCP entity is prepared to receive and service, meaningful only when bcpConfigMacSupport is enabled. This is the actual frame-format choice being negotiated, distinguishing canonical, Ethernet-style, address bit ordering from non-canonical, Token-Ring-style, ordering, so choosing the wrong one for the actual LAN segment attached would cause every bridged frame's addresses to be misinterpreted as bit-reversed garbage even though the link itself works. A half-bridge actually connected to a Token Ring segment but misconfigured with the Ethernet canonical type would forward frames whose MAC addresses appear scrambled to devices on the far end.