Which VLAN is the one whose traffic travels untagged on a trunk port?

Which VLAN is the one whose traffic travels untagged on a trunk port?

• A. Voice VLAN
• B. Data VLAN
• C. Native VLAN
• D. Management VLAN

Answer: (C)

On a trunk link, traffic from multiple VLANs is carried using 802.1Q tagging, but one VLAN’s frames are sent without a tag. That untagged VLAN is the native VLAN. Since the frames for the native VLAN traverse the link without a tag, they’re identified as belonging to that VLAN on the other end by virtue of being untagged. All other VLANs’ traffic is tagged with their VLAN IDs to keep them separate on the same physical link. So the VLAN whose traffic travels untagged on a trunk is the native VLAN. By default, many devices treat VLAN 1 as the native VLAN, though changing it and keeping both ends consistent is a common security practice.

On a trunk link, traffic from multiple VLANs is carried using 802.1Q tagging, but one VLAN’s frames are sent without a tag. That untagged VLAN is the native VLAN. Since the frames for the native VLAN traverse the link without a tag, they’re identified as belonging to that VLAN on the other end by virtue of being untagged. All other VLANs’ traffic is tagged with their VLAN IDs to keep them separate on the same physical link. So the VLAN whose traffic travels untagged on a trunk is the native VLAN. By default, many devices treat VLAN 1 as the native VLAN, though changing it and keeping both ends consistent is a common security practice.