Which statement describes 802.1Q tagging for inter-VLAN routing?

Which statement describes 802.1Q tagging for inter-VLAN routing?

• A. Each VLAN has its own subinterface with a VLAN tag on the trunk; the switch-to-router link carries tagged frames for all VLANs.
• B. All frames on the trunk are untagged.
• C. The router must use a separate physical interface for each VLAN.
• D. Tagging is only used on access ports.

Answer: (A)

802.1Q tagging lets multiple VLANs share one physical link by tagging frames with a VLAN identifier, so a single connection can carry traffic for several VLANs. For inter-VLAN routing, the router’s connection is set up with subinterfaces, each tied to a different VLAN and configured with 802.1Q encapsulation for that VLAN. The switch-to-router link is a trunk, carrying frames from all VLANs, with each frame carrying its VLAN tag. The router then routes between the VLANs using these subinterfaces, which is the typical router-on-a-stick setup. This approach is more scalable than dedicating a separate physical router interface for each VLAN, and tagging on trunks—not on access ports—enables the VLANs to remain separated while sharing the same physical path.

802.1Q tagging lets multiple VLANs share one physical link by tagging frames with a VLAN identifier, so a single connection can carry traffic for several VLANs. For inter-VLAN routing, the router’s connection is set up with subinterfaces, each tied to a different VLAN and configured with 802.1Q encapsulation for that VLAN. The switch-to-router link is a trunk, carrying frames from all VLANs, with each frame carrying its VLAN tag. The router then routes between the VLANs using these subinterfaces, which is the typical router-on-a-stick setup. This approach is more scalable than dedicating a separate physical router interface for each VLAN, and tagging on trunks—not on access ports—enables the VLANs to remain separated while sharing the same physical path.