How does the PFE handle Layer 2 and Layer 3 traffic?

The correct answer highlights the way the Packet Forwarding Engine (PFE) processes and manages network traffic at different layers. The PFE is designed to maintain separate forwarding tables for Layer 2 (data link layer) and Layer 3 (network layer) traffic. This separation is crucial because Layer 2 traffic often relies on MAC addresses for switching within the same physical or virtual local area network, while Layer 3 traffic uses IP addresses for routing across different networks.

Maintaining distinct forwarding tables allows the PFE to efficiently handle the different requirements and protocols associated with each layer. For instance, Layer 2 switching can occur without the need to delve into Layer 3 routing processes, enabling faster packet processing and reducing the load on the control plane. This design optimally leverages hardware resources and ensures that both types of traffic are managed effectively, adhering to their operational characteristics.

Separating the forwarding tables ensures that the PFE can quickly determine the appropriate action for a frame or packet based on its Layer 2 or Layer 3 attributes, thereby enhancing performance and scalability.