A subinterface is a logical interface created on a single physical router interface that allows routing between VLANs (known as Router-on-a-Stick (ROAS)). This method is commonly used when only one physical router is available, allowing inter-VLAN communication without additional hardware.

•Why not the other options?

•VXLAN (B) – This is used for extending Layer 2 networks over a Layer 3 infrastructure, primarily in data centers. It does not directly enable inter-VLAN communication.

•Layer 3 switch (C) – A Layer 3 switch can route between VLANs, but the scenario states that purchasing additional hardware is not an option.

•VIR (D) – This is not a standard networking term in the context of VLAN communication.