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Difficulty: EasyVLAN Configuration and 802.1Q Trunking

A network technician is configuring an IEEE 802.1Q trunk link between two switch ports. Which of the following statements accurately describe the behavior and configuration requirements of the native VLAN on an 802.1Q trunk? (Select TWO.)

  1. Frames associated with the native VLAN are transmitted across the trunk link without an 802.1Q header tag.Answer
  2. The native VLAN ID configuration must match on both connected switch interfaces to prevent frame misdirection.Answer
  3. C
    Devices assigned to the native VLAN can communicate with other VLANs on the switch without a Layer 3 routing device.
  4. D
    An 802.1Q trunk automatically applies a mandatory 4-byte tag header to frames from all configured VLANs, including the native VLAN.

Answer

The correct statements are that frames belonging to the native VLAN are sent untagged across the 802.1Q trunk, and both switches on the trunk link must be configured with matching native VLAN IDs.
IEEE 802.1Q trunk links carry native VLAN traffic in an untagged state by default. Because receiving switch ports place untagged frames into their locally configured native VLAN, both ends of the trunk link must agree on the same native VLAN number to preserve proper network isolation.

Step-by-Step Solution

1
Analyze standard IEEE 802.1Q tagging behavior for native vs. tagged VLANs.
IEEE 802.1Q inserts a 4-byte VLAN tag into Ethernet frames for all non-native VLANs, while native VLAN frames are transmitted untagged.
This untagged capability provides backward compatibility for legacy hubs or untagged device connections.
2
Evaluate the operational requirement for matching native VLAN settings across switches.
If Switch 1 sends untagged frames from native VLAN 10, Switch 2 will place incoming untagged frames into its configured native VLAN.
A mismatch causes untagged frames sent by one VLAN to leak into a different VLAN on the opposite side of the trunk.

Key Concept

802.1Q Native VLAN Tagging and Matching Requirements
Estimated Time:1m 0s
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Topics

VLAN Configuration and 802.1Q Trunking

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