Ethernet Switching Modes Explained | Generated by AI

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Question: What are the main switching modes of Ethernet switches, primarily including direct switching and which of the following?

A. Indirect switching
B. Detection control switching
C. Fragment switching
D. Store-and-forward switching

Answer:

The correct answer is D. Store-and-forward switching

Explanation:

Ethernet switches mainly use the following data switching (forwarding) methods:

1. Cut-through switching (直接交换 / 直通交换)
   • The switch starts forwarding the frame as soon as it reads the destination MAC address (usually after receiving the first 6–14 bytes).
   • Fastest forwarding speed, lowest latency.
   • Disadvantage: May forward error frames (no full CRC check).
2. Store-and-forward switching (存储转发交换)
   • The switch receives the entire frame, performs a full CRC check, discards bad frames, then forwards valid frames.
   • Highest reliability, can filter error frames.
   • Disadvantage: Higher latency (must wait for the whole frame).
3. Fragment-free switching (改进直接交换 / 无碎片交换)
   • A compromise method: The switch waits to receive the first 64 bytes (to avoid collision fragments), then starts forwarding.
   • Balances speed and error filtering (filters most collision fragments but not all errors).

Correct classification in the question:

The two main and most commonly mentioned switching modes of Ethernet switches are:

• Direct switching (cut-through)
• Store-and-forward switching

Therefore, the answer should be D. Store-and-forward switching.

Why your answer C is incorrect:

• “分段交换” (fragment switching) is not one of the standard mainstream switching modes of Ethernet switches.
• The term “分段交换” is sometimes misused or appears in poorly translated questions, but it does not correspond to any standard Ethernet switch forwarding method. The closest related concept is “fragment-free”, but even that is usually called “改进直接交换” or “无碎片交换”, not “分段交换”.

Summary of standard Ethernet switch switching modes (most textbooks & certification exams):

• 直接交换（Cut-through）
• 存储转发交换（Store-and-forward）
• 改进直接交换 / 无碎片交换（Fragment-free）

The question asks for the mode that pairs with “直接交换”, which is 存储转发交换 → D.

References:

• None (standard Ethernet switching knowledge from IEEE 802.3, Cisco CCNA material, and common Chinese network engineering textbooks)

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