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Difficulty: MediumVLAN Configuration and 802.1Q Trunking

Match each 802.1Q switch interface configuration command with its corresponding operational behavior on an enterprise switch link.

  • switchport trunk native vlan 99Configures the interface to transmit and receive untagged traffic belonging to a designated non-default broadcast domain across the trunk.
  • switchport mode trunkForces the interface into permanent trunking mode while continuing to send Dynamic Trunking Protocol (DTP) negotiation frames.
  • switchport trunk allowed vlan 10,20Prunes all traffic from the trunk link except for tagged frames matching the explicitly specified VLAN identification numbers.
  • switchport nonegotiatePrevents the interface from sending Dynamic Trunking Protocol (DTP) frames while operating in trunking mode.

Answer

Matching pairs:
- 'switchport trunk native vlan 99' maps to 'Configures the interface to transmit and receive untagged traffic belonging to a designated non-default broadcast domain across the trunk.'
- 'switchport mode trunk' maps to 'Forces the interface into permanent trunking mode while continuing to send Dynamic Trunking Protocol (DTP) negotiation frames.'
- 'switchport trunk allowed vlan 10,20' maps to 'Prunes all traffic from the trunk link except for tagged frames matching the explicitly specified VLAN identification numbers.'
- 'switchport nonegotiate' maps to 'Prevents the interface from sending Dynamic Trunking Protocol (DTP) frames while operating in trunking mode.'
Each command directly aligns with standard 802.1Q trunk operational behaviors: native VLAN commands set the untagged broadcast domain, mode trunk forces 802.1Q encapsulation while keeping DTP active, allowed vlan restricts active VLAN IDs over the trunk, and nonegotiate suppresses DTP packets for enhanced security.

Step-by-Step Solution

1
Analyze 'switchport trunk native vlan 99'
Identified as setting the 802.1Q native VLAN parameter to VLAN 99.
802.1Q trunking sends traffic for the native VLAN without inserting an 802.1Q header tag.
2
Analyze 'switchport mode trunk'
Identified as configuring unconditional trunking.
Statically setting trunk mode overrides dynamic auto/desirable modes, though DTP packets are still emitted unless explicitly suppressed.
3
Analyze 'switchport trunk allowed vlan 10,20'
Identified as configuring VLAN pruning on the trunk.
By default, all VLANs (1-4094) are allowed on a trunk link unless filtered using the allowed VLAN parameter.
4
Analyze 'switchport nonegotiate'
Identified as disabling Dynamic Trunking Protocol (DTP).
Security best practices recommend disabling unnecessary negotiation protocols on manually configured trunk links.

Key Concept

802.1Q Trunking Interface Commands and Operational Behaviors
Estimated Time:1m 30s
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Topics

VLAN Configuration and 802.1Q Trunking

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