The answer is a physical layer issue causing the interface to flap. The log output shows the line protocol on GigabitEthernet0/0 transitioning between up and down states at precise 10-second intervals, which is the classic signature of line protocol flapping—a condition where the interface repeatedly loses and re-establishes Layer 1 or Layer 2 connectivity. On the Cisco CCNP ENARSI 300-410 exam, this pattern tests your ability to differentiate between physical-layer problems (like a bad cable, faulty SFP, or loose connection) and Layer 3 misconfigurations, since routing protocols alone rarely cause such rhythmic state changes. A common trap is to blame a keepalive mismatch or spanning tree issue, but the exact 10-second cycle points directly to a hardware fault rather than a protocol timer. Remember the memory tip: “Ten seconds, check the transceiver”—if the flap interval is consistent, suspect the physical medium first.
300-410 Network Logging and Syslog Practice Question
This 300-410 practice question tests your understanding of network logging and syslog. 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 runs the following command on Router R5:
R5# show logging | include %LINEPROTO-5-UPDOWN
*Mar 1 00:00:10.123: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
*Mar 1 00:00:20.456: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down
*Mar 1 00:00:30.789: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
*Mar 1 00:00:40.012: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down
*Mar 1 00:00:50.345: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
*Mar 1 00:01:00.678: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down
Based on this output, what is the most likely problem?
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
✓
There is a physical layer issue causing the interface to flap.
The output shows the line protocol on GigabitEthernet0/0 flapping every 10 seconds. This is a classic symptom of a flapping interface, often due to a physical issue (bad cable, faulty transceiver) or a Layer 2 problem (e.g., spanning tree topology changes, keepalive mismatch).
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 interface is administratively down.
Why it's wrong here
The interface is going up and down, not administratively down; that would show a different message.
✓
There is a physical layer issue causing the interface to flap.
Why this is correct
Repeated line protocol up/down messages indicate a flapping interface, typically due to physical or Layer 2 issues.
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.
✗
The interface is configured with a high bandwidth delay product.
Why it's wrong here
Bandwidth delay product does not cause flapping.
✗
The router is experiencing a high CPU load due to routing updates.
Why it's wrong here
High CPU might cause slow processing but not line protocol flapping every 10 seconds.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
The interface is going up and down, not administratively down; that would show a different message.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Network Logging and Syslog — This question tests Network Logging and Syslog — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: There is a physical layer issue causing the interface to flap. — The output shows the line protocol on GigabitEthernet0/0 flapping every 10 seconds. This is a classic symptom of a flapping interface, often due to a physical issue (bad cable, faulty transceiver) or a Layer 2 problem (e.g., spanning tree topology changes, keepalive mismatch).
What should I do if I get this 300-410 question wrong?
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
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