350-401 Question #604: Real Exam Question with Answer & Explanation

Question

In which two ways does TCAM differ from CAM? (Choose two.)

Options

• ACAM is used to make Layer 2 forwarding decisions, and TCAM is used for Layer 3 address lookups.
• BThe MAC address table is contained in CAM, and ACL and QoS Information Is stored in TCAM.
• CCAM Is used by routers for IP address lookups, and TCAM is used to make Layer 2 forwarding
• DCAM is used for software switching mechanisms, and TCAM Is used for hardware switching
• EThe MAC address table Is contained in TCAM, and ACL and QoS information is stored in CAM.

Explanation

TCAM vs CAM Explanation

CAM (Content Addressable Memory) is designed for exact-match lookups and is used for Layer 2 forwarding decisions, storing the MAC address table that switches use to forward frames. TCAM (Ternary CAM) extends this by supporting three states (0, 1, and wildcard/X), making it ideal for Layer 3 lookups and storing complex entries like ACLs, QoS policies, and routing tables - this is why A and B are correct.

• C is wrong because it reverses the roles - CAM handles Layer 2, not routers doing IP lookups.
• D is wrong because both CAM and TCAM are hardware-based mechanisms; neither is used for software switching.
• E is wrong because it swaps the storage locations - the MAC table lives in CAM, and ACL/QoS data lives in TCAM.

💡 Memory Tip: Think of the T in TCAM as "Three states" and "Top-layer" (Layer 3+). CAM = simple, exact match, Layer 2; TCAM = flexible, wildcard-capable, Layer 3 and beyond (ACLs, QoS).

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