What Is the Architectural Difference Between MAC Address Table and TCAM?

Switching / TCAM

What is the architectural difference between the MAC address table and TCAM?

  1. TCAM entries are stored for 600 seconds, and MAC address table entries are kept for 200 seconds.
  2. TCAM entries are populated using the ARP table, and the MAC address table is populated dynamically from outgoing frames.
  3. TCAM entries consist of VLAN, port ID and source MAC Address, and MAC address table entries consist of source MAC address end port ID.
  4. TCAM entries are composed of value, mask, and result, and MAC address table entries are composed of value and results. Source Reference Answer

Community Votes

D
100%

100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

The exam tests the ternary (three-part) structure of TCAM versus the binary two-part MAC table; the trap is confusing the fields or the purpose of each table.

Understand the key structural difference between MAC address tables and TCAM entries. The community agrees that TCAM uses value, mask, and result, while MAC address tables store value and result only.

Choosing option C, which incorrectly lists VLAN, port ID, and source MAC as TCAM fields; TCAM is a generic ternary structure (value+mask+result), not a specific set of MAC fields.

Community Discussion (3 comments)

pacman64 👍 3 Selected: D
The correct answer is D: TCAM entries are composed of value, mask, and result, and MAC address table entries are composed of value and results. Here's why: TCAM (Ternary Content Addressable Memory): - Uses a three-component structure: 1. Value: The data to match 2. Mask: Determines which bits to compare 3. Result: The action to take when matched - Allows for wildcard matching - Optimized for fast lookups in networking devices MAC Address Table: - Uses a simpler two-component structure: 1. Value: MAC address 2. Result: Port number/interface - Direct one-to-one mapping - No masking capability needed Why other options are incorrect: A) The timing values are incorrect, and timing isn't an architectural difference B) This describes population methods, not architectural differences C) This incorrectly describes the components of both structures
Telcoeric 👍 2
A: No. this is exactly backwards. B: No. EIGRP is considered a hybrid routing protocol. C: No. EIGRP uses DUAL, OSPF uses SPF. D: Yes. But poorly worded. External EIGRP has an AD of 170. Internal EIGRP has an AD of 90.
chiacche 👍 1
Example: TCAM: deny ip 192.168.1.0 0.0.0.255 any MAC: MAC Address Port 00:1A:2B:3C:4D:5E Gi0/1

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Expert Analysis

Why the Answer Is Correct

Option D correctly identifies the architectural difference. TCAM entries are composed of three parts: value (the data to match), mask (which bits to compare), and result (the action to take). This allows wildcard matching for ACLs and QoS. A MAC address table, by contrast, is a simple binary lookup table with only the value (MAC address) and result (outgoing port), used for forwarding decisions.

Why the Other Options Are Wrong

Option A is wrong because it suggests timer values, but those are not architectural differences and are not standard values. Option B incorrectly states that TCAM is populated using the ARP table and that the MAC address table is populated only from outgoing frames; TCAM can be populated from many sources, and MAC tables are learned from source MAC addresses in incoming frames. Option C is wrong because it lists VLAN, port ID, and source MAC as TCAM fields; those are fields in a MAC address table, not the general ternary structure of TCAM.

Community Comment Notes

Comment [1] provides a clear breakdown of the three TCAM components and explains why option D is correct, noting that TCAM allows wildcard matching and is optimized for fast lookups. Comment [3] gives a practical example showing a TCAM entry like "deny ip 192.168.1.0 0.0.0.255 any" versus a simple MAC table entry mapping a MAC address to an interface. Comment [2] appears misaligned with the question and irrelevant, discussing EIGRP and administrative distance, so it should be ignored.

Official Reference

Exam Strategy

Memorize the ternary (value, mask, result) structure of TCAM and the binary (value, result) structure of a MAC table. When you see TCAM questions, look for keywords like 'wildcard', 'mask', or 'action' to identify the correct answer quickly.

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