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Zorluk: ZorSwitching Concepts and VLANs

A network engineer is auditing Layer 2 forwarding operations, frame encapsulation rules, and switch security configurations on an enterprise switch stack. Match each switching concept or feature on the left with its precise operational behavior on the right.

  • IEEE 802.1Q Native VLAN ProcessingIngress untagged frames are assigned to a designated VLAN ID, while egress frames matching this VLAN ID are transmitted across the trunk without an 802.1Q header.
  • CAM Table Entry Aging ExpirationSubsequent unicast frames destined for an unlisted destination address are flooded out all active switch ports in the same VLAN except the receiving port.
  • Port Security in Sticky MAC ModeDynamically learned MAC addresses are written to the running configuration and persist across reboots if the configuration is saved.
  • PVST+ System ID ExtensionEmbeds the 12-bit VLAN identifier into the Bridge Priority field to differentiate Spanning Tree topology instances per VLAN.

Cevap

IEEE 802.1Q Native VLAN Processing matches with untagged ingress frame assignment and untagged egress trunk transmission. CAM Table Entry Aging Expiration matches with unknown unicast flooding out all same-VLAN ports except ingress. Port Security in Sticky MAC Mode matches with writing dynamically learned MAC addresses to the running configuration. PVST+ System ID Extension matches with embedding the 12-bit VLAN ID into the Bridge Priority field.
Each concept correctly matches its underlying Layer 2 mechanism: 802.1Q Native VLAN handles untagged frame forwarding across trunk links; CAM Table Expiration forces unknown unicast flooding within the VLAN boundary upon lookup misses; Sticky MAC Port Security writes dynamic MACs to running-config; and the PVST+ System ID Extension embeds the 12-bit VLAN identifier directly into the 16-bit Bridge Priority structure.

Adım Adım Çözüm

1
Analyze trunk port frame encapsulation mechanisms for 802.1Q native VLANs.
Identify that 802.1Q trunks do not tag frames originating from or destined to the native VLAN, leaving ingress/egress native VLAN frames untagged.
Backward compatibility with legacy non-tagging devices requires untagged frame processing on native VLANs.
2
Evaluate MAC address table aging behavior when a host goes silent.
Determine that CAM aging deletes unused entries, forcing the switch to treat subsequent traffic to that host as unknown unicast.
When a destination MAC address is missing from the switch lookup table, Layer 2 forwarding rules require flooding the frame across the local broadcast domain.
3
Differentiate between static, dynamic, and sticky port security configurations.
Confirm sticky learning automatically converts dynamic MAC address observations into saved running configuration lines.
Sticky MAC security eliminates manual static MAC entry while preventing unauthorized hardware swaps.
4
Examine PVST+ Spanning Tree Bridge ID structure.
Match the System ID Extension to the 12-bit VLAN ID field appended to the configurable bridge priority value.
PVST+ requires each VLAN to maintain an independent STP instance with a unique Bridge Identifier.

Anahtar Kavram

Layer 2 Switching Concepts, VLAN Encapsulation, Forwarding Tables, and Spanning Tree Architecture
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Konular

Switching Concepts and VLANs

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