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Difficulty: MediumSwitching Concepts and VLANs

Match each Layer 2 switching concept on the left with its corresponding operational description on the right.

  • 802.1Q TaggingInserts a 4-byte field containing a VLAN identifier into the Ethernet frame header across trunk links.
  • Native VLANCarries untagged frame traffic across a trunk link without appending a VLAN header.
  • Port SecurityRestricts switch port access based on MAC addresses and enforces configured security violation actions.
  • PortFastTransitions an access port immediately to the forwarding state, bypassing listening and learning states.

Answer

802.1Q Tagging matches inserting a 4-byte VLAN header; Native VLAN matches carrying untagged traffic; Port Security matches MAC address restriction; PortFast matches bypassing STP listening and learning states.
Each concept pairs directly with its functional definition: 802.1Q tagging adds VLAN identification headers over trunks, Native VLAN transports untagged frames, Port Security restricts access by MAC address, and PortFast bypasses intermediate STP convergence states for faster link availability.

Step-by-Step Solution

1
Analyze trunk encapsulation mechanisms.
802.1Q encapsulation modifies standard Ethernet frames by inserting a 4-byte VLAN header containing a 12-bit VLAN ID.
This allows switches to identify traffic belonging to specific VLANs across shared trunk connections.
2
Examine untagged frame handling over trunk lines.
Untagged frames belong to the Native VLAN, which transports them across 802.1Q trunks without adding headers.
Native VLAN configuration allows backward compatibility with legacy non-tagging switch ports and control protocols.
3
Evaluate Layer 2 access control features.
Port Security controls ingress traffic based on configured or dynamically learned MAC addresses.
It prevents unauthorized endpoints from sending traffic by taking restrict, protect, or shutdown actions upon violation.
4
Review Spanning Tree Protocol (STP) convergence optimization.
PortFast enables immediate transition to the forwarding state for edge ports.
Edge connections to end-user workstations do not form switching loops, making listening and learning delays unnecessary.

Key Concept

Switching Concepts and VLAN Operations
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Topics

Switching Concepts and VLANs

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