Which of the following actions may a switch take on data frames?

Question

Options

• Adiscard
• Bblock
• Cflood
• Dforward

• A
  81% (21)
• B
  19% (5)

Explanation

A network switch has exactly three actions it can perform on a data frame: discard (drop the frame due to errors, filtering rules, or when the source and destination are on the same segment), flood (send the frame out all ports except the incoming one when the destination MAC address is unknown or for broadcasts), and forward (send the frame out a specific port when the destination MAC is found in the switch's MAC address table). These three actions represent the complete decision set a switch makes after looking up a frame's destination MAC address.

Why B (block) is wrong: "Block" is a Spanning Tree Protocol (STP) port state, not an action a switch takes on a frame. A port in STP blocking state simply doesn't participate in data forwarding - the switch isn't actively doing something to the frame; the port itself is disabled for traffic. This is a common trap because "block" sounds intuitive.

Memory tip: Think "FDF" - Flood, Discard, Forward" - the three things a switch does to frames. When the MAC is known → Forward; when unknown/broadcast → Flood; when there's an error or it needs to be dropped → Discard. "Block" belongs to STP port states, not frame handling - if you see it in a frame-action question, it's the distractor.

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