Which of the following boards can be blocked by running the BLK BRD command?

The BLK BRD (Block Board) command is a Maintenance and Measurement Language (MML) command used to administratively block a board within the Baseband Unit (BBU). This command is specifically designed for boards slotted into the BBU chassis, such as a Baseband Processing Unit (BBP). Blocking a board gracefully takes it out of service, preventing it from processing traffic and allowing for safe removal or maintenance. The other options are not boards in the BBU chassis that are managed using the BLK BRD command.

B. DUPEU: This is a power and environment interface unit. It is not a processing board and is managed with different commands; blocking it would affect the BBU's power.
C. AAU: An Active Antenna Unit is an external radio and antenna module. It is managed as a radio unit (RU), typically using commands like BLK RU.
D. RRU: A Remote Radio Unit is an external radio module. Like an AAU, it is managed as an RU, not as a board within the BBU chassis.

1. Huawei Technologies Co., Ltd. (2023). 3900 & 5900 Series Base Station MML Command Reference. Section: Device Maintenance Commands. This reference explicitly lists the BLK BRD command and specifies its usage for boards within the BBU, with the BBP being a primary example of a target board.

2. Huawei Technologies Co., Ltd. (2021). BBU5900 Hardware Description. Section: BBU Boards. This document distinguishes between internal boards like the BBP and external units like RRUs/AAUs, clarifying the management domain for board-level commands.