CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. A key principle to apply: a switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.. 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.
A switchport connected to another switch should carry VLANs 10, 20, and 30. The interface is operational, but only VLAN 10 works. VLANs 20 and 30 fail. Which explanation is most likely if the port was accidentally configured as an access port in VLAN 10?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The interface is carrying only VLAN 10 because an access port does not transport multiple VLANs like a trunk.
The correct answer is A because an access port is limited to a single VLAN, so only VLAN 10 traverses the link. Option B is incorrect: IP subnet masks are irrelevant on switchports that operate at Layer 2. Option C is incorrect: inter-switch links typically use trunk ports, not routed ports. Option D is incorrect: STP does not block based on VLAN IDs; it blocks redundant paths, not specific VLANs.
Key principle: A switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The interface is carrying only VLAN 10 because an access port does not transport multiple VLANs like a trunk.
Why this is correct
This is correct because an access-port misconfiguration explains why only the configured VLAN works.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
A switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.
✗
VLAN 20 and 30 require different IP subnet masks on the switches.
Why it's wrong here
This is wrong because the immediate problem is the Layer 2 switchport role, not IP mask design.
When this WOULD be correct
In a different scenario, if the question stated that VLANs 20 and 30 were configured with different subnet masks that did not match the corresponding VLAN interfaces on the switches, then this option would be correct. This would imply that the mismatched subnet masks are preventing proper communication for those VLANs.
✗
Every inter-switch link must use a routed port instead of a trunk.
Why it's wrong here
This is wrong because trunks are the normal mechanism for carrying multiple VLANs between switches.
When this WOULD be correct
In a question where the requirement specifies that all inter-switch links must operate at Layer 3, and the context indicates that routed ports are necessary for communication between VLANs, this option would be correct. For example, if the question stated that the switches are configured for routing between VLANs instead of switching.
✗
STP blocks all VLANs except VLAN 10 by design.
Why it's wrong here
This is wrong because STP does not inherently permit only one VLAN simply because it is VLAN 10.
When this WOULD be correct
In a different scenario where a question states that STP is configured to block all VLANs except for a designated VLAN due to specific network policies, option D would be correct. For example, if a network engineer intentionally configured STP to prioritize VLAN 10 for critical traffic while blocking others for security reasons.
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.
✓The interface is carrying only VLAN 10 because an access port does not transport multiple VLANs like a trunk.Correct answer▾
Why this is correct
This is correct because an access-port misconfiguration explains why only the configured VLAN works.
✗VLAN 20 and 30 require different IP subnet masks on the switches.Wrong answer — click to see why▾
Why this is wrong here
IP subnet masks are Layer 3 concepts and do not affect Layer 2 VLAN propagation across a switchport. The issue here is purely Layer 2, related to the switchport mode (access vs. trunk), not IP addressing. VLANs 20 and 30 would still fail regardless of subnet mask configuration.
★ When this WOULD be the correct answer
In a different scenario, if the question stated that VLANs 20 and 30 were configured with different subnet masks that did not match the corresponding VLAN interfaces on the switches, then this option would be correct. This would imply that the mismatched subnet masks are preventing proper communication for those VLANs.
Why candidates choose this
Students might confuse VLAN configuration with IP subnetting, thinking that different VLANs require different subnet masks on the switches. However, VLANs are Layer 2 constructs and do not depend on IP subnet masks for their operation.
✗Every inter-switch link must use a routed port instead of a trunk.Wrong answer — click to see why▾
Why this is wrong here
Routed ports are Layer 3 interfaces used for routing between networks, not for carrying multiple VLANs. The standard method for carrying multiple VLANs between switches is to use a trunk port, which tags frames with VLAN IDs. A routed port would not solve the issue and would break Layer 2 connectivity.
★ When this WOULD be the correct answer
In a question where the requirement specifies that all inter-switch links must operate at Layer 3, and the context indicates that routed ports are necessary for communication between VLANs, this option would be correct. For example, if the question stated that the switches are configured for routing between VLANs instead of switching.
Why candidates choose this
Some students may think that routed ports are more advanced or flexible, but they are not designed for VLAN trunking. The confusion arises from the term 'routed' versus 'switched' ports, but trunks are the correct mechanism for inter-switch VLAN transport.
✗STP blocks all VLANs except VLAN 10 by design.Wrong answer — click to see why▾
Why this is wrong here
STP (Spanning Tree Protocol) prevents loops by blocking redundant paths, but it does not selectively block specific VLANs based on their VLAN ID. If STP were blocking VLANs 20 and 30, it would be due to a misconfiguration like PVST+ inconsistencies, not by design. The scenario describes a simple access port misconfiguration, not an STP issue.
★ When this WOULD be the correct answer
In a different scenario where a question states that STP is configured to block all VLANs except for a designated VLAN due to specific network policies, option D would be correct. For example, if a network engineer intentionally configured STP to prioritize VLAN 10 for critical traffic while blocking others for security reasons.
Why candidates choose this
Students might associate STP with VLAN blocking, especially in the context of Per-VLAN Spanning Tree (PVST+), where STP runs per VLAN. However, STP does not inherently block all VLANs except VLAN 10; it would only block specific ports to prevent loops, not arbitrarily drop VLANs.
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
Be careful not to confuse access port limitations with trunk configuration issues. Always verify the port mode when troubleshooting VLAN connectivity.
Detailed technical explanation
How to think about this question
VLANs (Virtual Local Area Networks) segment a physical switch into multiple logical networks, allowing traffic separation at Layer 2. Switchports can be configured as access ports or trunk ports. An access port carries traffic for a single VLAN, tagging none or one VLAN ID, typically used for end devices. A trunk port, however, carries traffic for multiple VLANs simultaneously by tagging frames with VLAN IDs using protocols like IEEE 802.1Q, enabling inter-switch VLAN communication.
When connecting two switches that must share multiple VLANs, the interface must be configured as a trunk port. This configuration allows VLANs 10, 20, and 30 to traverse the link. If the port is mistakenly set as an access port assigned to VLAN 10, it will only forward untagged frames for VLAN 10 and drop or ignore traffic from VLANs 20 and 30. This misconfiguration causes VLAN 20 and 30 traffic to fail despite the physical link being operational.
This scenario is a common exam trap where candidates confuse access and trunk port roles. Practically, an access port restricts traffic to a single VLAN, so multi-VLAN communication between switches requires trunking. The exam tests understanding of VLAN tagging and port modes, emphasizing that an access port cannot carry multiple VLANs, which is essential for inter-switch links in VLAN-segmented networks.
KKey Concepts to Remember
A switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.
A trunk port uses IEEE 802.1Q tagging to carry multiple VLANs simultaneously across a single physical link between switches.
Inter-switch links that must transport multiple VLANs require trunk ports to allow VLAN traffic segregation and forwarding.
Configuring an inter-switch link as an access port limits traffic to the assigned VLAN, blocking all other VLANs from passing.
VLAN tagging is essential for switches to identify and forward frames belonging to different VLANs over trunk links.
A misconfigured access port on an inter-switch link causes VLAN traffic other than the access VLAN to fail, despite link status being up.
Understanding the difference between access and trunk port modes is critical for proper VLAN design and troubleshooting in Cisco networks.
Switchport mode misconfiguration is a common cause of VLAN communication failures in multi-VLAN environments.
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 switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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 switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs., then practise related 200-301 questions on the same topic to reinforce the concept.
Switching and Network Access — This question tests Switching and Network Access — A switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs..
What is the correct answer to this question?
The correct answer is: The interface is carrying only VLAN 10 because an access port does not transport multiple VLANs like a trunk. — The correct answer is A because an access port is limited to a single VLAN, so only VLAN 10 traverses the link. Option B is incorrect: IP subnet masks are irrelevant on switchports that operate at Layer 2. Option C is incorrect: inter-switch links typically use trunk ports, not routed ports. Option D is incorrect: STP does not block based on VLAN IDs; it blocks redundant paths, not specific VLANs.
What should I do if I get this 200-301 question wrong?
Review a switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
A switchport configured as an access port carries traffic for only one VLAN and does not tag frames with VLAN IDs.
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