Which Cisco switching mechanism requires a Cisco router to process all packets in the CPU?
- process switching
- circuit switching
- Cisco Express Forwarding
- fast switching
- pass-through switching
Explanation: Process switching is the slowest switching mechanism because every packet is examined by the CPU and all forwarding decisions are made in software. For every individual frame, the router must use its CPU to strip the Layer 2 header, look up the Layer 3 destination in the routing table, and rewrite the Layer 2 header. Due to this high demand on the processor, it is considered the most CPU-intensive method and is typically used only as a last resort or for troubleshooting.
In contrast, other mechanisms are more efficient:
- Fast switching only requires the CPU to examine the first packet in a flow to create a cache for subsequent packets.
- Cisco Express Forwarding (CEF) is the fastest method and is less CPU-intensive because it uses hardware-based tables (FIB and adjacency tables) to switch all packets in a flow, including the first one, without needing to involve the CPU for each frame.
Related exam: Modules 1 – 7: Checkpoint Exam: Network Switching Answers (CCNP ENCOR v9)
