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Difficulty: MediumVLAN Configuration and 802.1Q Trunking

Match each VLAN configuration concept or 802.1Q trunking parameter on the left with its corresponding operational behavior or frame-handling mechanism on the right.

  • Native VLAN ConfigurationDesignates the VLAN context used to send and receive untagged traffic across an 802.1Q trunk interface.
  • 802.1Q Header TaggingInserts a 4-byte field containing a 12-bit VLAN Identifier (VID) into the standard Ethernet frame.
  • Trunk Allowed VLAN ListRestricts traffic forwarding across a trunk link exclusively to explicitly permitted VLAN IDs.
  • Voice VLAN FeatureAllows a switch interface to carry tagged VoIP traffic while maintaining untagged data traffic for a connected device.

Answer

Native VLAN Configuration corresponds to designating the VLAN context used for untagged traffic. 802.1Q Header Tagging corresponds to inserting a 4-byte field containing a 12-bit VLAN Identifier (VID). Trunk Allowed VLAN List corresponds to restricting traffic forwarding exclusively to explicitly permitted VLAN IDs. Voice VLAN Feature corresponds to allowing an interface to carry tagged VoIP traffic while maintaining untagged data traffic.
Each trunking concept is correctly matched to its defined network behavior: Native VLAN manages untagged trunk traffic, 802.1Q header tagging adds the 4-byte frame modifier with 12-bit VID, the trunk allowed list filters permitted VLAN IDs across links, and Voice VLAN enables dual tagged/untagged traffic handling on access ports.

Step-by-Step Solution

1
Analyze Native VLAN functionality on 802.1Q trunks
Identified that native VLAN handles untagged frame transmission across trunks.
By default in 802.1Q, frames belonging to the native VLAN are sent across trunk links without adding an 802.1Q header tag.
2
Analyze 802.1Q tagging structure
Identified the 4-byte insertion containing the 12-bit VID.
IEEE 802.1Q modifies the Ethernet frame by inserting a 4-byte tag field between the Source MAC Address and EtherType fields.
3
Analyze allowed VLAN list configuration
Identified trunk filtering behavior based on permitted VLAN IDs.
By default, trunks permit VLANs 1-4094; configuring an allowed list explicitly restricts which VLAN broadcast domains extend across the link.
4
Analyze Voice VLAN operational model
Identified dual-VLAN behavior on access ports supporting IP phones.
Voice VLAN allows single physical access ports to separate real-time tagged voice traffic from untagged desktop data traffic.

Key Concept

802.1Q Trunking Protocols and Port Characteristics
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Topics

VLAN Configuration and 802.1Q Trunking

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