What is the difference between CEF and process switching?

Question

Options

• ACEF processes packets that are too complex for process switching to manage.
• BCEF is more CPU-intensive than process switching.
• CCEF uses the FIB and the adjacency table to make forwarding decisions, whereas process
• DProcess switching is faster than CEF.

• A
  2% (1)
• B
  2% (1)
• C
  96% (45)

Explanation

CEF vs. Process Switching Explained

Option C is correct because CEF (Cisco Express Forwarding) uses two pre-built data structures - the Forwarding Information Base (FIB) and the adjacency table - to make rapid forwarding decisions without CPU intervention, while process switching requires the CPU to look up the routing table for every single packet, making it far slower and more resource-intensive.

Why the distractors are wrong:

• Option A is incorrect because CEF actually handles simpler, high-volume forwarding tasks more efficiently; it's not designed for "complex" packets that process switching can't handle - in fact, some complex packets fall back to process switching.
• Option B is the opposite of reality - CEF is less CPU-intensive because forwarding decisions are made using cached tables rather than repeated routing table lookups.
• Option D is also backwards - CEF is significantly faster than process switching, which is why CEF is the default switching method on modern Cisco routers.

Memory Tip: Think of CEF like a GPS with a saved route (FIB + adjacency table = pre-calculated path), while process switching is like looking at a paper map for every turn - same destination, but one is clearly faster!

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