- A
The connected switch port is administratively down.
The switch port in administratively down state causes the router's line protocol to stay down because no Layer 2 connectivity can be established.
- B
Mismatched encapsulation types on the router and switch.
Why wrong: Encapsulation mismatch for trunk links can cause line protocol down, but the scenario explicitly mentions that the switch port is administratively down, making this the primary cause.
- C
Speed and duplex mismatch between the router and switch.
Why wrong: Speed/duplex mismatches can result in performance problems, errors, or even line protocol down on some platforms, but the given fact that the switch port is administratively down rules out any active negotiation or mismatch.
- D
Incorrect native VLAN configuration on the trunk link.
Why wrong: A native VLAN mismatch on a trunk link can cause line protocol issues, but there is no indication that the link is a trunk, and the switch port being administratively down is a more direct cause.
Quick Answer
The answer is that the connected switch port being administratively down is the most likely cause. This is because the router’s interface shows Layer 1 is up—meaning the physical cable and hardware are functioning—but the line protocol is down, which indicates a failure at Layer 2. Since the switch port is in a shutdown state, it does not send keepalive frames or negotiate a link, so the router’s line protocol cannot activate even after the no shutdown command is issued. On the CCNA 200-301 v2 exam, this scenario tests your ability to interpret show interfaces output and distinguish between Layer 1 and Layer 2 issues; a common trap is to assume the router’s own interface is still shut down when the output clearly says “up.” A useful memory tip is “Layer 1 up, Layer 2 down? Check the other end’s shutdown.”
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.
A network engineer notices that after issuing the no shutdown command on interface GigabitEthernet0/0 of a router, the interface remains down. The output of show interfaces GigabitEthernet0/0 displays 'GigabitEthernet0/0 is up, line protocol is down'. The physically connected switch port is also administratively down. What is the most likely cause?
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 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 connected switch port is administratively down.
The show interfaces output indicates that the router interface is physically up (Layer 1 is functional) but the line protocol is down (Layer 2 is not active). The most common cause for this specific combination is that the connected switch port is administratively down (shutdown), which prevents the switch from sending any keepalive frames or establishing a link. Since the switch port is not forwarding traffic, the router's line protocol cannot come up, even though the router interface itself is no longer in shutdown mode.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 connected switch port is administratively down.
Why this is correct
The switch port in administratively down state causes the router's line protocol to stay down because no Layer 2 connectivity can be established.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Mismatched encapsulation types on the router and switch.
Why it's wrong here
Encapsulation mismatch for trunk links can cause line protocol down, but the scenario explicitly mentions that the switch port is administratively down, making this the primary cause.
- ✗
Speed and duplex mismatch between the router and switch.
Why it's wrong here
Speed/duplex mismatches can result in performance problems, errors, or even line protocol down on some platforms, but the given fact that the switch port is administratively down rules out any active negotiation or mismatch.
- ✗
Incorrect native VLAN configuration on the trunk link.
Why it's wrong here
A native VLAN mismatch on a trunk link can cause line protocol issues, but there is no indication that the link is a trunk, and the switch port being administratively down is a more direct cause.
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 connected switch port is administratively down.Correct answer▾
Why this is correct
The switch port in administratively down state causes the router's line protocol to stay down because no Layer 2 connectivity can be established.
✗Mismatched encapsulation types on the router and switch.Wrong answer — click to see why▾
Why this is wrong here
Candidates often attribute line protocol down to encapsulation issues, missing the clear indication that the switch port is shut down.
✗Speed and duplex mismatch between the router and switch.Wrong answer — click to see why▾
Why this is wrong here
Duplex mismatch is a common cause of interface issues, so candidates may assume it without considering the explicitly stated admin-down condition.
✗Incorrect native VLAN configuration on the trunk link.Wrong answer — click to see why▾
Why this is wrong here
Candidates may recall VLAN mismatch as a cause for line protocol down on trunk links, forgetting that the scenario gives a clear admin-down 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: answer the scenario, not the keyword
Cisco often tests the distinction between 'administratively down' on the local device versus the remote device; candidates may mistakenly think that issuing 'no shutdown' on the router is sufficient, overlooking that the remote switch port must also be enabled for the line protocol to come up.
Trap categories for this question
Scenario analysis trap
Encapsulation mismatch for trunk links can cause line protocol down, but the scenario explicitly mentions that the switch port is administratively down, making this the primary cause.
Detailed technical explanation
How to think about this question
When a switch port is administratively down, it does not send any Ethernet frames, including link pulses or keepalives, so the router's physical layer (carrier detect) may still see the cable as connected but the switch will not respond to any Layer 2 signaling. The router's line protocol relies on receiving valid frames (e.g., keepalives in HDLC or PPP) from the remote end; without them, the protocol state remains down. In a real-world scenario, this often occurs after a switch port is accidentally left in shutdown during maintenance, while the router interface is enabled, leading to a one-sided administrative state mismatch.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The connected switch port is administratively down. — The show interfaces output indicates that the router interface is physically up (Layer 1 is functional) but the line protocol is down (Layer 2 is not active). The most common cause for this specific combination is that the connected switch port is administratively down (shutdown), which prevents the switch from sending any keepalive frames or establishing a link. Since the switch port is not forwarding traffic, the router's line protocol cannot come up, even though the router interface itself is no longer in shutdown mode.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 200-301
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network technician replaced a faulty SFP transceiver on a switch port. After replacement, the port remains in a down/down state. The technician verifies the fiber cable is securely connected at both ends and observes that the remote switch port is also in a down/down state. What should the technician do next?
hard- A.Verify that the speed and duplex settings are set to auto-negotiation.
- B.Check whether the SFP module type is incompatible with the switch.
- C.Verify the VLAN assignment on the port.
- ✓ D.Check the running configuration for the no shutdown command on the interface.
Why D: The correct answer is D because the most common cause of a port remaining in a down/down state after replacing a faulty SFP is that the interface is administratively down. The 'no shutdown' command must be applied to bring the interface up. Since the technician already verified physical connectivity and both ends show down/down, the issue is likely at the configuration layer, not the physical layer.
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Last reviewed: Jun 25, 2026
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