- A
The physical interface GigabitEthernet0/1 was administratively down.
This is correct because the physical interface must be in an 'up/up' state for subinterfaces to function. Even if the subinterface is configured with 'no shutdown', the physical interface being administratively down (missing 'no shutdown') prevents any traffic from passing.
- B
The VLAN 10 subinterface was configured with the wrong encapsulation dot1q VLAN ID.
Why wrong: This is incorrect because the question states that the interface configuration appears correct, implying encapsulation is properly set. A wrong VLAN ID would cause the subinterface to not match the VLAN, but the issue is that the subinterface is not operational at all.
- C
The switch port connected to R1 was not configured as a trunk.
Why wrong: This is incorrect because the question states the switch trunk port allows VLANs 10 and 20, implying the trunk is correctly configured. A non-trunk port would cause connectivity issues, but the subinterface would still be operational on R1.
- D
The VLAN 10 subinterface was missing the 'no shutdown' command.
Why wrong: This is incorrect because subinterfaces inherit the administrative state from the physical interface. Even if the subinterface has 'no shutdown', it cannot be operational if the physical interface is administratively down.
Quick Answer
The answer is that the physical interface GigabitEthernet0/1 was administratively down. This is correct because a subinterface inherits its operational state from the parent physical interface; even if the subinterface has a "no shutdown" command applied, it cannot function if the physical interface itself is in a shutdown state. On the CCNA 200-301 v2 exam, this scenario tests your understanding of the hierarchical relationship between physical interfaces and subinterfaces in router-on-a-stick configurations—a common trap is to assume that configuring the subinterface alone is sufficient. Remember that the physical interface must be "no shutdown" before any subinterface can pass traffic; a quick "show interfaces status" will reveal the administratively down condition. Memory tip: "Parent first, child second—if the parent sleeps, the child can't speak."
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
You are connected to the console of R1. The network administrator reports that hosts on VLAN 10 cannot ping the default gateway (192.168.10.1). R1's GigabitEthernet0/1 is connected to a switch with trunk port allowing VLAN 10 and 20. The interface configuration on R1 appears correct, but the VLAN 10 interface is not operational.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The physical interface GigabitEthernet0/1 was administratively down.
The GigabitEthernet0/1 interface was administratively down (missing 'no shutdown' in the initial config). Although the subinterface had 'no shutdown', the physical interface must also be up. Bringing up the physical interface resolved the issue.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 physical interface GigabitEthernet0/1 was administratively down.
Why this is correct
This is correct because the physical interface must be in an 'up/up' state for subinterfaces to function. Even if the subinterface is configured with 'no shutdown', the physical interface being administratively down (missing 'no shutdown') prevents any traffic from passing.
Related concept
Access ports place end devices into a single VLAN.
- ✗
The VLAN 10 subinterface was configured with the wrong encapsulation dot1q VLAN ID.
Why it's wrong here
This is incorrect because the question states that the interface configuration appears correct, implying encapsulation is properly set. A wrong VLAN ID would cause the subinterface to not match the VLAN, but the issue is that the subinterface is not operational at all.
- ✗
The switch port connected to R1 was not configured as a trunk.
Why it's wrong here
This is incorrect because the question states the switch trunk port allows VLANs 10 and 20, implying the trunk is correctly configured. A non-trunk port would cause connectivity issues, but the subinterface would still be operational on R1.
- ✗
The VLAN 10 subinterface was missing the 'no shutdown' command.
Why it's wrong here
This is incorrect because subinterfaces inherit the administrative state from the physical interface. Even if the subinterface has 'no shutdown', it cannot be operational if the physical interface is administratively down.
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 physical interface GigabitEthernet0/1 was administratively down.Correct answer▾
Why this is correct
This is correct because the physical interface must be in an 'up/up' state for subinterfaces to function. Even if the subinterface is configured with 'no shutdown', the physical interface being administratively down (missing 'no shutdown') prevents any traffic from passing.
✗The VLAN 10 subinterface was configured with the wrong encapsulation dot1q VLAN ID.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the subinterface would still show as up/up (though traffic would not be forwarded) if the encapsulation were wrong; the problem is the physical interface being down.
Why candidates choose this
Candidates often confuse encapsulation mismatches with interface state issues, assuming a misconfigured VLAN ID causes the interface to be down.
✗The switch port connected to R1 was not configured as a trunk.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the switch trunk configuration is given as correct; the problem is on the router side, not the switch.
Why candidates choose this
Candidates may think the issue is on the switch side because trunk misconfiguration is a common cause of VLAN connectivity problems.
✗The VLAN 10 subinterface was missing the 'no shutdown' command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that subinterfaces do not have an independent administrative state; they rely on the physical interface being up.
Why candidates choose this
Candidates often assume subinterfaces need their own 'no shutdown' and overlook the physical interface state.
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: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The physical interface GigabitEthernet0/1 was administratively down. — The GigabitEthernet0/1 interface was administratively down (missing 'no shutdown' in the initial config). Although the subinterface had 'no shutdown', the physical interface must also be up. Bringing up the physical interface resolved the issue.
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 7, 2026
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