A Layer 3 switch is the optimal solution when multiple VLANs must intercommunicate while maintaining high performance and minimal hardware complexity. CompTIA A+ explains that Layer 3 switches combine the capabilities of switching (Layer 2) and routing (Layer 3), allowing VLAN traffic to be routed internally at wire speed, without the latency typically associated with traditional routers.
Layer 3 switches use hardware-based routing, meaning they forward inter-VLAN traffic using ASICs (Application-Specific Integrated Circuits). This allows them to achieve extremely fast throughput, ideal for environments like computer training institutes where multiple VLANs may be used for student labs, instructor networks, and administrative traffic.
A router (D) can route between VLANs but introduces more latency due to software-based routing and typically requires additional equipment. A Web application firewall (A) and DDoS appliance (B) are security devices unrelated to internal VLAN communication.
Because the institute requires minimal hardware and high-speed inter-VLAN communication, the Layer 3 switch is the only CompTIA-supported device that meets both requirements simultaneously.