Which of the following descriptions about the working principle of a Layer 2 switch are correct? (Multiple choice)

Question

Options

• ALayer 2 switches can improve network performance by maintaining the MAC table and forwarding
• BDifferent broadcast domains such as interfaces effectively isolate broadcast domain conflicts in the
• CMAC entries in the switch will be permanently recorded
• DLayer 2 switches forward data packets based on MAC addresses

• A
  71% (22)
• C
  29% (9)

Explanation

Layer 2 switches learn MAC addresses by inspecting incoming frames and build a MAC address table, allowing them to forward traffic only out the correct port rather than flooding all ports - this is why A is correct and directly improves network performance. D is correct because MAC-address-based forwarding is the defining characteristic of Layer 2 operation. B is correct because each switch port creates its own collision domain, so devices on separate ports never contend for the same wire, eliminating collision-related congestion (the question wording appears garbled, but this is the intended principle).

C is wrong because MAC table entries are not permanent - switches use an aging timer (typically 300 seconds by default) and purge entries for MAC addresses they haven't heard from recently, keeping the table fresh and accurate.

Memory tip: Think of the switch as a smart postal worker who keeps a temporary address book (MAC table with aging). It reads the destination on each envelope (D), learns return addresses as they arrive (A), and gives each mailbox its own slot so nobody fights over the same box (B) - but it eventually discards old addresses it hasn't seen in a while, so the book never becomes permanent (why C is false).

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