The correct answer is that the switch MAC address table helps reduce unnecessary flooding when the destination MAC is known. This is because the switch builds the table by learning which source MAC addresses arrive on which ports, then uses that mapping to forward frames only to the specific port associated with the destination MAC, rather than broadcasting the frame out every port. On the CCNA 200-301 v2 exam, this concept tests your understanding of Layer 2 switching fundamentals, often appearing in questions about how a switch handles unknown unicast frames versus known unicast frames. A common trap is confusing the MAC address table with a routing table or assuming it stores Layer 3 information like OSPF neighbor data or DHCP leases—it does not. Remember the memory tip: “Learn the MAC, send it back” — the switch learns the source MAC on ingress and forwards only to the destination MAC’s egress port, cutting down on unnecessary flooding.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: a switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which two statements accurately describe the role of a switch MAC address table?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It maps learned MAC addresses to switch ports for local forwarding decisions.
A switch MAC address table helps the switch make local forwarding decisions efficiently. In plain language, the switch learns which MAC addresses appear on which ports and then uses that information to send frames only where they need to go instead of flooding every frame everywhere.
The MAC table is not the same thing as a routing table, and it is not used for OSPF neighbor storage or DHCP lease records.
Key principle: A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
It maps learned MAC addresses to switch ports for local forwarding decisions.
Why this is correct
This is correct because that is the core purpose of the MAC address table.
Related concept
A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
✓
It helps reduce unnecessary flooding when the destination MAC is known.
Why this is correct
This is correct because once a destination MAC is known, the switch can forward more selectively.
Related concept
A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
✗
It stores the best Layer 3 routes to remote networks.
Why it's wrong here
This is wrong because routing tables, not MAC tables, handle Layer 3 path decisions.
When this WOULD be correct
This option would be correct in a question that asks about the functions of a router's routing table, which does store the best Layer 3 routes to remote networks based on various routing protocols.
✗
It contains the router’s OSPF authentication keys.
Why it's wrong here
This is wrong because MAC tables do not store OSPF security information.
When this WOULD be correct
In a question focused on router configurations, if asked about the components of OSPF and their roles, option D could be correct if it specifically inquires about where OSPF authentication keys are stored within a router's configuration.
In a question asking about DHCP functionality, such as 'What mechanism is used to assign IP addresses dynamically to end hosts on a network?', option E would be correct as it directly relates to the role of DHCP servers in IP address allocation.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓It maps learned MAC addresses to switch ports for local forwarding decisions.Correct answer▾
Why this is correct
This is correct because that is the core purpose of the MAC address table.
✗It stores the best Layer 3 routes to remote networks.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because a switch MAC address table does not store Layer 3 routing information; it specifically maps Layer 2 MAC addresses to switch ports for local traffic forwarding.
★ When this WOULD be the correct answer
This option would be correct in a question that asks about the functions of a router's routing table, which does store the best Layer 3 routes to remote networks based on various routing protocols.
Why candidates choose this
Candidates might choose this option due to confusion between Layer 2 and Layer 3 functionalities, as both involve addressing but serve different purposes in network operations.
✗It contains the router’s OSPF authentication keys.Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because a switch MAC address table does not store OSPF authentication keys; it is designed to map MAC addresses to switch ports for forwarding decisions within a Layer 2 network.
★ When this WOULD be the correct answer
In a question focused on router configurations, if asked about the components of OSPF and their roles, option D could be correct if it specifically inquires about where OSPF authentication keys are stored within a router's configuration.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of the roles of different network devices, confusing the functions of switches and routers, especially in the context of routing protocols like OSPF.
✗It assigns IP addresses to end hosts dynamically.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because a switch MAC address table does not handle IP address assignments; it specifically deals with mapping MAC addresses to switch ports for local traffic forwarding.
★ When this WOULD be the correct answer
In a question asking about DHCP functionality, such as 'What mechanism is used to assign IP addresses dynamically to end hosts on a network?', option E would be correct as it directly relates to the role of DHCP servers in IP address allocation.
Why candidates choose this
Candidates may find this option tempting due to the association of switches with network connectivity and the common misconception that switches also manage IP address assignments, leading to confusion between Layer 2 and Layer 3 functionalities.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Avoid confusing the MAC address table with routing tables or ARP tables, which involve IP addresses and routing information.
Detailed technical explanation
How to think about this question
A switch MAC address table is a fundamental component in Layer 2 switching that maps MAC addresses to specific switch ports. When a switch receives a frame, it examines the source MAC address and records which port the frame arrived on. This learning process builds the MAC address table dynamically, enabling the switch to forward frames intelligently. Instead of broadcasting frames to all ports, the switch uses the MAC address table to send frames only to the port associated with the destination MAC address, optimizing network efficiency.
The MAC address table supports local forwarding decisions by associating each learned MAC address with a single switch port. When a frame arrives destined for a known MAC address, the switch consults the table and forwards the frame only to the corresponding port, reducing unnecessary flooding. If the destination MAC address is unknown, the switch floods the frame out all ports except the source port, ensuring delivery while learning new MAC addresses. This behavior contrasts with routing tables, which operate at Layer 3 and determine paths to remote networks.
A common exam trap is confusing the MAC address table with routing or security functions. The MAC table does not store Layer 3 routes, OSPF authentication keys, or DHCP assignments. Instead, it strictly manages MAC-to-port mappings for local switching. Practically, this means that switches efficiently forward Ethernet frames within the same broadcast domain, while routers handle inter-network traffic. Understanding this distinction helps avoid misinterpreting the MAC table’s role and prevents errors on the CCNA exam.
KKey Concepts to Remember
A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
The MAC address table enables the switch to forward frames only to the port associated with the destination MAC address, reducing unnecessary network flooding.
If the destination MAC address is unknown, the switch floods the frame out all ports except the source port to ensure delivery and learn new MAC addresses.
The MAC address table operates at Layer 2 and is distinct from routing tables, which handle Layer 3 path selection to remote networks.
Switches do not use the MAC address table to store OSPF authentication keys or any Layer 3 routing protocol security information.
Dynamic Host Configuration Protocol (DHCP) assigns IP addresses and is unrelated to the MAC address table’s function of MAC-to-port mapping.
Efficient MAC address table management improves network performance by minimizing broadcast traffic and localizing frame forwarding.
The MAC address table is essential for VLAN-aware switches to maintain separate MAC address mappings per VLAN, ensuring proper traffic segregation.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review a switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table..
What is the correct answer to this question?
The correct answer is: It maps learned MAC addresses to switch ports for local forwarding decisions. — A switch MAC address table helps the switch make local forwarding decisions efficiently. In plain language, the switch learns which MAC addresses appear on which ports and then uses that information to send frames only where they need to go instead of flooding every frame everywhere.
The MAC table is not the same thing as a routing table, and it is not used for OSPF neighbor storage or DHCP lease records.
What should I do if I get this 200-301 question wrong?
Review a switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A switch learns MAC addresses dynamically by recording the source MAC and the ingress port of received frames into its MAC address table.
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