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Difficulty: MediumVLAN Configuration and 802.1Q Trunking

A network engineer is provisioning switch interface profiles across an enterprise network that includes desktop workstations, IP phones, and inter-switch links. Match each switchport configuration command on the left with its corresponding operational frame behavior on the right.

  • switchport mode accessStrips 802.1Q headers on egress and assigns all untagged ingress frames to a single specific broadcast domain.
  • switchport trunk native vlan 50Transmits and receives untagged frames on an 802.1Q trunk for the specified VLAN while requiring 4-byte tags for all other VLANs.
  • switchport trunk allowed vlan 10,20Restricts trunk traffic by permitting 802.1Q tagged frames matching specified IDs and discarding untagged or unlisted VLAN traffic.
  • switchport voice vlan 30Enables an interface to process untagged data traffic from an attached workstation alongside 802.1Q tagged traffic from an auxiliary device.

Answer

Matching pairs: 'switchport mode access' pairs with single broadcast domain untagged handling; 'switchport trunk native vlan 50' pairs with untagged frame processing for specified ID on 802.1Q trunk; 'switchport trunk allowed vlan 10,20' pairs with restricting trunk traffic to permitted tagged VLAN IDs; 'switchport voice vlan 30' pairs with processing untagged data traffic alongside tagged IP telephony traffic.
Each switchport parameter maps directly to its 802.1Q framing specification: access ports strip headers for single VLAN endpoints, native VLAN commands dictate which trunk traffic remains untagged, allowed lists control 802.1Q tag filtering, and voice VLAN allows simultaneous tagged voice and untagged data traffic.

Step-by-Step Solution

1
Analyze standard access port behavior.
Identified that access ports belong to one VLAN and do not retain 802.1Q tags when delivering frames to endpoint devices.
Endpoint devices such as standard PCs expect untagged Ethernet II frames.
2
Analyze 802.1Q native VLAN operation.
Matched native VLAN configuration to the rule specifying untagged frame transmission/reception across an 802.1Q trunk.
By default in 802.1Q, one VLAN per trunk is designated to carry untagged frames to maintain backward compatibility.
3
Analyze allowed VLAN list configuration.
Associated the allowed VLAN statement with frame filtering that limits trunk traversal to explicitly permitted VLAN IDs.
Trunk pruning and security filtering restrict broadcast domains from spanning unnecessary switch links.
4
Analyze voice VLAN port behavior.
Linked auxiliary voice VLAN setup to multi-VLAN access port operation handling untagged PC data and tagged voice traffic.
IP phones act as mini-switches, tagging their own VoIP traffic while bridging untagged workstation frames.

Key Concept

802.1Q VLAN Frame Identification and Port Modes
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Topics

VLAN Configuration and 802.1Q Trunking

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