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Difficulty: MediumSwitching Concepts and VLANs

A network administrator is designing switch port profiles and configuring advanced Virtual Local Area Network (VLAN) feature sets across enterprise switches. Match each switching concept on the left with its correct operational description on the right.

  • Native VLANCarries control plane frames and all untagged Layer 2 traffic across an 802.1Q trunk link without adding an explicit VLAN header.
  • PortFastBypasses Spanning Tree Protocol (STP) listening and learning states to place an access port immediately into the forwarding state.
  • Voice VLANSegregates IP telephony packets onto a designated VLAN and assigns 802.1p Class of Service (CoS) priority tags to protect call quality.
  • Isolated Port (Private VLAN)Restricts switch traffic so the interface can only communicate with promiscuous ports, blocking direct frame exchange with other isolated or community ports.

Answer

Native VLAN matches carrying untagged frames over an 802.1Q trunk; PortFast matches bypassing STP listening/learning states for immediate forwarding; Voice VLAN matches segregating IP telephony traffic and applying 802.1p CoS priority tags; Isolated Port matches restricting traffic so communication occurs strictly with promiscuous ports.
Each concept correctly maps to its core operational behavior: Native VLAN handles untagged trunk traffic, PortFast eliminates STP delays on edge ports, Voice VLAN handles prioritized telephony frames, and Isolated Ports restrict Layer 2 host-to-host connectivity strictly to promiscuous default gateways.

Step-by-Step Solution

1
Identify the operation of 802.1Q trunking regarding untagged traffic
Native VLAN handles untagged traffic across trunk links without modifying Ethernet headers.
802.1Q trunks tag frames belonging to specified VLANs but leave Native VLAN traffic untagged for backward compatibility and control plane transport.
2
Analyze Spanning Tree Protocol optimization features for access ports
PortFast transitions edge interfaces directly into the forwarding state.
End-user hosts do not create Layer 2 loops, so skipping listening and learning prevents DHCP timeout issues when devices boot up.
3
Examine traffic handling for VoIP endpoints connected to access ports
Voice VLAN isolates telephony packets and enforces 802.1p priority.
VoIP applications require minimal latency and jitter, which is achieved by separating traffic into a Voice VLAN with Quality of Service tags.
4
Evaluate Layer 2 isolation boundaries within Private VLANs (PVLANs)
An Isolated Port can only send/receive traffic to/from promiscuous ports.
Private VLAN isolated ports prevent peer-to-peer compromise by blocking frame forwarding between endpoints assigned to the same isolated VLAN segment.

Key Concept

Switching Concepts and VLAN Technologies (802.1Q Trunking, PortFast, Voice VLAN, Private VLANs)
Estimated Time:1m 30s
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Topics

Switching Concepts and VLANs

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