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Question

Difficulty: MediumSwitching Concepts and VLANs

A network technician is reviewing Layer 2 switch forwarding modes and port auto-negotiation behaviors. Match each switching operation or port feature on the left with its corresponding functional description on the right.

  • Store-and-Forward SwitchingBuffers the complete Ethernet frame and verifies the Frame Check Sequence (FCS) CRC prior to forwarding.
  • Cut-Through SwitchingReads only the 6-byte destination MAC address before immediately forwarding the frame to achieve minimum latency.
  • Fragment-Free SwitchingInspects the first 64 bytes of an Ethernet frame to ensure collision fragments are discarded before forwarding.
  • Auto-MDIXAutomatically detects cable interface requirements and internally swaps transmit and receive pairs.

Answer

Store-and-Forward Switching matches buffering the full frame and verifying the FCS CRC. Cut-Through Switching matches reading only the destination MAC address for minimal latency. Fragment-Free Switching matches inspecting the first 64 bytes to eliminate collision fragments. Auto-MDIX matches automatically detecting cable pinouts and swapping transmit/receive pairs.
Store-and-Forward buffers the full frame for FCS validation; Cut-Through forwards after inspecting only the 6-byte destination MAC; Fragment-Free inspects 64 bytes to drop collision fragments; Auto-MDIX automatically configures internal transmit/receive pinouts based on connected cabling.

Step-by-Step Solution

1
Identify full-frame validation switching behavior
Store-and-Forward buffers the entire frame to calculate the Frame Check Sequence CRC, ensuring invalid frames are dropped.
Full frame buffering provides maximum reliability at the expense of slight latency.
2
Identify ultra-low latency forwarding behavior
Cut-Through reads only the destination MAC address (6 bytes) before immediately forwarding.
Minimal preamble/address inspection yields the lowest possible forwarding delay.
3
Identify collision fragment mitigation behavior
Fragment-Free inspects the first 64 bytes, which is where collision fragments occur in half-duplex Ethernet.
This serves as a compromise between cut-through speed and basic collision filtering.
4
Identify physical interface pinout automation
Auto-MDIX electronically adjusts pin functions to allow straight-through or crossover cables interchangeably.
Automated physical layer detection eliminates wiring mismatched connections.

Key Concept

Switch Frame Forwarding Methods and Auto-MDIX
Estimated Time:1m 30s
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Topics

Switching Concepts and VLANs

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