350-401 Question #1034: Real Exam Question with Answer & Explanation

Question

What is the benefit of using TCAM for IP forwarding decisions versus using the CAM table?

Options

• ATCAM finds results based on binary, and CAM uses the longest match to find results
• BTCAM processes lookups in a hardware CPU. and CAM relies on binary masks to find results.
• CTCAM finds results based on masks, and CAM finds results basing on exact match.
• DTCAM uses low cost hardware memory to store addresses, and CAM uses expensive hardware

Explanation

TCAM vs CAM for IP Forwarding

Wait - there's an issue with the marked answer. Option C is actually the correct answer, not B. TCAM (Ternary CAM) uses a third state (0, 1, or "don't care"/wildcard masks) to perform longest-prefix match lookups for IP routing, while standard CAM only performs exact binary matches - making TCAM ideal for routing tables where subnet masks must be evaluated.

Why the distractors are wrong:

• Option A is backwards - CAM uses binary exact matching, not longest-match; TCAM handles mask-based lookups
• Option B (marked as correct) is factually wrong - TCAM is a hardware memory structure, not a CPU process; it performs lookups in parallel at wire speed without CPU involvement
• Option D is misleading - TCAM is actually the more expensive memory type due to its additional circuitry for the ternary (three-state) logic

Memory Tip: Think of the "T" in TCAM as "Three-state" (0, 1, wildcard) - this ternary capability is what allows mask-based subnet matching for routing, while regular CAM only knows binary yes/no exact matches used in MAC address (switching) lookups.

⚠️ Flag this question to your instructor - the listed correct answer (B) appears to be an error.

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