IEEE VLAN tagging configuration: Which command sets a switch port to use the IEEE 802.1Q trunk encapsulation standard?
Networking
Virtual LANs
Difficulty: Easy
Choose an option
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ASwitch(config)# switchport trunk encapsulation isl
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BSwitch(config)# switchport trunk encapsulation ietf
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CSwitch(config)# switchport trunk encapsulation dot1q
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DSwitch(config-if)# switchport trunk encapsulation isl
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ESwitch(config-if)# switchport trunk encapsulation dot1q
Answer
Correct Answer: Switch(config-if)# switchport trunk encapsulation dot1q
Explanation
Introduction / Context:IEEE 802.1Q is the standard method of VLAN tagging. Cisco switches must be configured to use ISL (Cisco proprietary) or 802.1Q.
Given Data / Assumptions:
- We want to use IEEE standard VLAN tagging.
- Correct IOS syntax is required.
Concept / Approach:Interface configuration mode is needed. The keyword “dot1q” corresponds to 802.1Q tagging.
Step-by-Step Solution:
Enter interface config mode.Command: switchport trunk encapsulation dot1q.Applies 802.1Q tagging to that trunk port.Verification / Alternative check:Run show interface trunk to confirm encapsulation.
Why Other Options Are Wrong:
- ISL: Cisco proprietary, not IEEE.
- IETF: Not valid syntax in IOS.
- Global config mode syntax is wrong; must be under interface.
Common Pitfalls:Entering command in global mode instead of interface mode.
Final Answer:Switch(config-if)# switchport trunk encapsulation dot1q