Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A switchport is configured as an access port for VLAN 20, but users connected to it cannot reach the default gateway. The switch shows the interface as up/up. Which switch misconfiguration is the most likely cause?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The access port is missing a speed command
Distractor.
B
Best answer
VLAN 20 has not been created on the switch
Correct choice.
C
Distractor review
The switch has not enabled VTP transparent mode
Distractor.
D
Distractor review
The port should use DTP desirable mode
Distractor.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that an interface showing up/up means the port is fully functional and correctly forwarding traffic. Candidates may overlook the necessity of creating the VLAN in the switch’s VLAN database. Without VLAN 20 existing, the switch cannot forward traffic for that VLAN, even though the physical link is active. This leads to confusion because the interface status does not reflect VLAN misconfiguration, causing users to lose connectivity to the default gateway despite the port appearing operational.
Technical deep dive
How to think about this question
VLANs (Virtual Local Area Networks) segment a physical switch into multiple logical broadcast domains, allowing traffic separation and improved network management. Each VLAN is identified by a VLAN ID and must be explicitly created in the switch's VLAN database. Access ports are configured to assign all incoming untagged frames to a specific VLAN, ensuring hosts connected to these ports communicate within that VLAN's broadcast domain. When a switchport is configured as an access port for VLAN 20, the switch expects VLAN 20 to exist in its VLAN database. If VLAN 20 has not been created, the switch cannot associate the port's traffic with a valid VLAN. Although the physical interface may show as up/up, indicating the link is operational, the Layer 2 forwarding process fails because the VLAN context is missing. This results in hosts connected to that port being unable to reach devices outside their local segment, such as the default gateway. This scenario is a common exam trap because the interface status can mislead candidates into thinking the port is fully operational. However, VLAN configuration is critical for Layer 2 forwarding. The practical impact is that traffic is dropped silently, causing connectivity issues. Network engineers must verify VLAN existence and proper assignment to access ports to ensure correct Layer 2 communication and avoid such silent failures.
KKey Concepts to Remember
- A switchport configured as an access port assigns all incoming traffic to a single VLAN, which must exist in the VLAN database to forward traffic correctly.
- If a VLAN is not created on the switch, any port assigned to that VLAN will not forward traffic properly, even if the interface status shows up/up.
- The switch uses the VLAN database to map VLAN IDs to VLAN names and parameters, which is essential for Layer 2 forwarding and communication within that VLAN.
- Traffic from hosts connected to an access port assigned to a non-existent VLAN will be dropped, causing loss of connectivity to devices such as the default gateway.
- The physical interface state (up/up) indicates Layer 1 and Layer 2 link status but does not guarantee correct VLAN configuration or Layer 2 forwarding.
- VTP transparent mode controls VLAN propagation between switches but does not affect VLAN existence on a single switch; missing VLANs must be created locally.
- Dynamic Trunking Protocol (DTP) modes like desirable are irrelevant for access ports, which do not negotiate trunking and only carry untagged frames for one VLAN.
- Speed commands on access ports affect physical link speed but do not impact VLAN membership or Layer 2 forwarding related to VLAN configuration.
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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Question 2
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Question 3
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Question 4
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Question 5
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Question 6
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FAQ
Questions learners often ask
What does this 200-301 question test?
A switchport configured as an access port assigns all incoming traffic to a single VLAN, which must exist in the VLAN database to forward traffic correctly.
What is the correct answer to this question?
The correct answer is: VLAN 20 has not been created on the switch — If the access port is assigned to VLAN 20 but VLAN 20 does not exist in the VLAN database, traffic is not placed into a usable VLAN and hosts lose connectivity. The port can still appear physically up while forwarding fails at Layer 2.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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