Which network configuration uses a single physical router interface with multiple sub-interfaces, one per VLAN, to route traffic between VLANs over a trunk link?

Which network configuration uses a single physical router interface with multiple sub-interfaces, one per VLAN, to route traffic between VLANs over a trunk link?

• A. Layer 3 Switch
• B. BPDU Guard
• C. Router on a Stick
• D. Port Security

Answer: (C)

Router on a stick is a method where a single physical router interface is split into multiple logical sub-interfaces, each tied to a different VLAN. A trunk link carries traffic for all those VLANs, with each sub-interface configured for 802.1Q tagging. Each sub-interface has its own IP address in its VLAN, acting as the default gateway for hosts in that VLAN. The router then routes traffic between the VLANs across that trunk. This setup is exactly what the description calls out: one router interface handling multiple VLANs through sub-interfaces to perform inter-VLAN routing on a trunk. The other options don’t describe this configuration. BPDU Guard is a Spanning Tree security feature, and Port Security restricts which devices can connect to a switch port. A Layer 3 switch can perform inter-VLAN routing as well, but it typically uses SVIs or dedicated routed ports rather than a single router interface with per-VLAN sub-interfaces.

Router on a stick is a method where a single physical router interface is split into multiple logical sub-interfaces, each tied to a different VLAN. A trunk link carries traffic for all those VLANs, with each sub-interface configured for 802.1Q tagging. Each sub-interface has its own IP address in its VLAN, acting as the default gateway for hosts in that VLAN. The router then routes traffic between the VLANs across that trunk. This setup is exactly what the description calls out: one router interface handling multiple VLANs through sub-interfaces to perform inter-VLAN routing on a trunk.

The other options don’t describe this configuration. BPDU Guard is a Spanning Tree security feature, and Port Security restricts which devices can connect to a switch port. A Layer 3 switch can perform inter-VLAN routing as well, but it typically uses SVIs or dedicated routed ports rather than a single router interface with per-VLAN sub-interfaces.