IEEE VLAN tagging configuration: Which command sets a switch port to use the IEEE 802.1Q trunk encapsulation standard?

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:

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