Which VLAN characteristic is true for VLAN tagging across trunks?

Which VLAN characteristic is true for VLAN tagging across trunks?

• A. All switches support 802.1Q tagging
• B. The tag is only used on wireless links
• C. The tag is not required for trunking
• D. The tag is only used on VLAN 1

Answer: (A)

VLAN tagging on trunks uses a standardized method (802.1Q) to attach a VLAN ID to each frame so multiple VLANs can share a single physical link between switches. Because 802.1Q is the standard, virtually all modern switches support it, allowing trunk links to carry traffic for many VLANs simultaneously. On a trunk, frames for the native VLAN can be sent untagged, while frames for all other VLANs are tagged, which explains why tagging isn’t needed for every single frame but is required to carry multiple VLANs across the same link. Tagging isn’t limited to wireless links, and it isn’t exclusive to VLAN 1. That’s why the statement about universal 802.1Q support on switches best captures how VLAN tagging across trunks works.

VLAN tagging on trunks uses a standardized method (802.1Q) to attach a VLAN ID to each frame so multiple VLANs can share a single physical link between switches. Because 802.1Q is the standard, virtually all modern switches support it, allowing trunk links to carry traffic for many VLANs simultaneously. On a trunk, frames for the native VLAN can be sent untagged, while frames for all other VLANs are tagged, which explains why tagging isn’t needed for every single frame but is required to carry multiple VLANs across the same link. Tagging isn’t limited to wireless links, and it isn’t exclusive to VLAN 1. That’s why the statement about universal 802.1Q support on switches best captures how VLAN tagging across trunks works.