200-301 Question #571: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An engineer is asked to insert the new VLAN into the existing trunk without modifying anything previously configured. Which command accomplishes this task?

Options

• Aswitchport trunk allowed vlan 100-104
• Bswitchport trunk allowed vlan add 104
• Cswitchport trunk allowed vlan all
• Dswitchport trunk allowed vlan 104

Explanation

To add a new VLAN to an existing trunk link without modifying or removing previously configured allowed VLANs, the add keyword must be used with the switchport trunk allowed vlan command.

Common mistakes.

• A. switchport trunk allowed vlan 100-104 would replace the entire existing allowed VLAN list with only VLANs 100 through 104, potentially removing other important VLANs.
• C. switchport trunk allowed vlan all would allow all VLANs (1-4094) on the trunk, which is a significant change to the existing configuration and may introduce security risks.
• D. switchport trunk allowed vlan 104 would replace the entire existing allowed VLAN list with only VLAN 104, thereby removing any other previously allowed VLANs.

Concept tested. VLAN trunking configuration (allowed vlan add)

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swvlan.html

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