CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: a trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.. 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 trunk link between two switches is operational, but one side shows a native VLAN mismatch warning. What is the main concern with that condition?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Untagged traffic may be associated with different VLANs on each end of the trunk
A native VLAN mismatch can cause untagged traffic to be interpreted as belonging to different VLANs on each end of the trunk. In plain language, the two switches disagree about where untagged frames belong. That can lead to confusing traffic behavior, reachability problems for certain flows, and operational warnings. It is not always a total outage, but it is a design inconsistency that should be corrected.
This matters because trunks carry multiple VLANs, and the native VLAN defines how untagged traffic is handled. If both ends do not agree, the logical treatment of those frames becomes inconsistent. The correct answer is the one that focuses on misclassification of untagged traffic, not on unrelated routing behavior.
Key principle: A trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Untagged traffic may be associated with different VLANs on each end of the trunk
Why this is correct
This is correct because that is the direct risk of a native VLAN mismatch.
Related concept
A trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.
✗
All tagged VLAN traffic is automatically converted to routed traffic
Why it's wrong here
This is wrong because a native VLAN mismatch does not convert the trunk into a Layer 3 routed link.
When this WOULD be correct
In a question focused on VLAN configuration and routing protocols, where the context involves a scenario of VLAN tagging and routing behavior, this option could be correct if it specifically states that tagged traffic is being routed due to a misconfiguration, leading to confusion in the network.
✗
The mismatch forces OSPF adjacency reset on all routers
Why it's wrong here
This is wrong because the condition described is a trunking issue, not an OSPF-specific mechanism.
When this WOULD be correct
If the question were about the impact of VLAN mismatches on OSPF routing protocols, specifically asking how such mismatches can disrupt OSPF neighbor relationships, this option could be correct. For example, if the question stated that a native VLAN mismatch could lead to OSPF adjacency issues due to improper handling of untagged traffic, then this option would apply.
✗
The trunk can carry only one VLAN until the mismatch is cleared
Why it's wrong here
This is wrong because other tagged VLANs may still pass even though the native mismatch is a problem.
When this WOULD be correct
In a different scenario, if the question specified that the trunk link was configured to allow only a single VLAN due to a specific policy or configuration, then this option could be correct. For example, if the question stated that the trunk was intended to support only a management VLAN, the mismatch could lead to confusion about which VLAN is being carried.
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.
✓Untagged traffic may be associated with different VLANs on each end of the trunkCorrect answer▾
Why this is correct
This is correct because that is the direct risk of a native VLAN mismatch.
✗All tagged VLAN traffic is automatically converted to routed trafficWrong answer — click to see why▾
Why this is wrong here
A native VLAN mismatch does not convert tagged traffic into routed traffic. Tagged frames continue to be switched based on their VLAN tags, and the trunk remains a Layer 2 link. The mismatch only affects untagged frames on the native VLAN.
★ When this WOULD be the correct answer
In a question focused on VLAN configuration and routing protocols, where the context involves a scenario of VLAN tagging and routing behavior, this option could be correct if it specifically states that tagged traffic is being routed due to a misconfiguration, leading to confusion in the network.
Why candidates choose this
Students might confuse the native VLAN mismatch with a scenario where the trunk is misconfigured as a routed port, or they may think that the mismatch causes the trunk to behave like a Layer 3 link. However, trunk ports remain Layer 2 regardless of native VLAN issues.
✗The mismatch forces OSPF adjacency reset on all routersWrong answer — click to see why▾
Why this is wrong here
A native VLAN mismatch is a Layer 2 trunking issue and does not directly affect OSPF or any routing protocol. OSPF adjacency is a Layer 3 process and would only be impacted if the mismatch caused connectivity loss for the router interfaces, but the mismatch itself does not force OSPF adjacency resets.
★ When this WOULD be the correct answer
If the question were about the impact of VLAN mismatches on OSPF routing protocols, specifically asking how such mismatches can disrupt OSPF neighbor relationships, this option could be correct. For example, if the question stated that a native VLAN mismatch could lead to OSPF adjacency issues due to improper handling of untagged traffic, then this option would apply.
Why candidates choose this
Students might associate any VLAN mismatch with routing protocol issues because they have seen scenarios where VLAN misconfigurations lead to routing problems. However, the native VLAN mismatch specifically does not trigger OSPF events.
✗The trunk can carry only one VLAN until the mismatch is clearedWrong answer — click to see why▾
Why this is wrong here
A native VLAN mismatch does not prevent the trunk from carrying other tagged VLANs. Tagged frames for other VLANs are still forwarded correctly because they are not affected by the native VLAN configuration. The trunk can carry multiple VLANs, but the native VLAN traffic is misdirected.
★ When this WOULD be the correct answer
In a different scenario, if the question specified that the trunk link was configured to allow only a single VLAN due to a specific policy or configuration, then this option could be correct. For example, if the question stated that the trunk was intended to support only a management VLAN, the mismatch could lead to confusion about which VLAN is being carried.
Why candidates choose this
Students might think that any mismatch on a trunk would cause the entire trunk to fail or limit its functionality. However, the native VLAN mismatch only affects untagged traffic, not the entire trunk.
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 native VLAN mismatches with general trunk failures or issues affecting tagged traffic.
Detailed technical explanation
How to think about this question
A trunk link in Cisco networking carries traffic for multiple VLANs between switches, using tagging to differentiate VLAN frames. The native VLAN is a special VLAN on a trunk port where untagged frames are assigned. By default, Cisco switches use VLAN 1 as the native VLAN, but this can be changed for security or design reasons. When a native VLAN mismatch occurs, one switch associates untagged frames with one VLAN, while the other switch associates them with a different VLAN, causing inconsistent frame handling.
The native VLAN mismatch warning indicates that the native VLAN IDs configured on each end of the trunk do not match. This mismatch causes untagged traffic to be misclassified, potentially leading to traffic leaks, broadcast storms, or security vulnerabilities. The trunk still carries tagged VLAN traffic correctly, but untagged frames are at risk of being sent to the wrong VLAN, disrupting communication and network segmentation. Cisco switches generate syslog warnings to alert administrators to this condition.
In practice, the native VLAN mismatch does not convert the trunk into a routed link nor does it directly affect routing protocols like OSPF. The main operational impact is on Layer 2 VLAN tagging consistency. The exam trap is to confuse native VLAN mismatch effects with routing or protocol adjacency issues. Understanding that the mismatch affects only untagged traffic classification helps avoid this mistake and ensures proper trunk configuration and VLAN isolation in Cisco environments.
KKey Concepts to Remember
A trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.
The native VLAN defines how untagged frames are handled on a trunk port and must match on both ends to avoid traffic misclassification.
A native VLAN mismatch causes untagged traffic to be assigned to different VLANs on each switch, leading to inconsistent Layer 2 forwarding.
Cisco switches generate native VLAN mismatch warnings in syslog to alert administrators of potential VLAN tagging issues on trunks.
Tagged VLAN traffic continues to pass normally despite a native VLAN mismatch, but untagged traffic may be misrouted or lost.
Native VLAN mismatches do not convert trunk links into Layer 3 routed links and do not directly impact routing protocols like OSPF.
Proper trunk configuration requires matching native VLAN IDs on both ends to maintain VLAN segmentation and prevent security risks.
Ignoring native VLAN mismatches can cause broadcast storms, VLAN leaks, and unpredictable network behavior in Cisco switched networks.
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 trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.
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 trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames., 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 trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames..
What is the correct answer to this question?
The correct answer is: Untagged traffic may be associated with different VLANs on each end of the trunk — A native VLAN mismatch can cause untagged traffic to be interpreted as belonging to different VLANs on each end of the trunk. In plain language, the two switches disagree about where untagged frames belong. That can lead to confusing traffic behavior, reachability problems for certain flows, and operational warnings. It is not always a total outage, but it is a design inconsistency that should be corrected.
This matters because trunks carry multiple VLANs, and the native VLAN defines how untagged traffic is handled. If both ends do not agree, the logical treatment of those frames becomes inconsistent. The correct answer is the one that focuses on misclassification of untagged traffic, not on unrelated routing behavior.
What should I do if I get this 200-301 question wrong?
Review a trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A trunk link carries multiple VLANs between switches by tagging frames except for the native VLAN, which sends untagged frames.
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