200-901 Infrastructure and Automation Practice Question
This 200-901 practice question tests your understanding of infrastructure and automation. 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.
Exhibit
Refer to the exhibit.
ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet1 10.1.1.1 YES NVRAM up up
GigabitEthernet2 unassigned YES unset up up
Serial0/0/0 192.168.1.1 YES NVRAM up down
Loopback0 1.1.1.1 YES NVRAM up up
Refer to the exhibit. Based on the output, which interface is experiencing a Layer 2 issue?
Refer to the exhibit.
ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet1 10.1.1.1 YES NVRAM up up
GigabitEthernet2 unassigned YES unset up up
Serial0/0/0 192.168.1.1 YES NVRAM up down
Loopback0 1.1.1.1 YES NVRAM up up
A
Loopback0
Why wrong: Both Status and Protocol are up.
B
GigabitEthernet1
Why wrong: Both Status and Protocol are up.
C
Serial0/0/0
Protocol is down while Status is up, indicating a Layer 2 issue.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Serial0/0/0
The output shows that Serial0/0/0 is in the 'down/down' state, which indicates a Layer 1 or Layer 2 issue. Since the serial interface is administratively up (not 'administratively down'), the 'down/down' status points to a Layer 2 problem, such as a missing keepalive, encapsulation mismatch, or loss of carrier detect (CD) signal, rather than a Layer 3 addressing or routing issue.
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.
✗
Loopback0
Why it's wrong here
Both Status and Protocol are up.
✗
GigabitEthernet1
Why it's wrong here
Both Status and Protocol are up.
✓
Serial0/0/0
Why this is correct
Protocol is down while Status is up, indicating a Layer 2 issue.
Related concept
Read the scenario before looking for a memorised answer.
✗
GigabitEthernet2
Why it's wrong here
Both Status and Protocol are up.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 'up/down' (Layer 1 issue) and 'down/down' (Layer 2 issue), and candidates mistakenly assume any 'down' status is a Layer 1 problem without checking the line protocol state.
Detailed technical explanation
How to think about this question
In Cisco IOS, the 'show interfaces' command displays the line protocol status as the second field; 'down/down' means both the physical layer (carrier) and the data-link layer (e.g., HDLC keepalives, PPP LCP) have failed. For serial interfaces, common Layer 2 issues include encapsulation mismatch (e.g., HDLC vs PPP), missing clock rate on the DCE side, or a faulty cable causing loss of CD signal. This contrasts with 'up/down', which indicates a Layer 1 issue where the physical link is active but the data-link protocol cannot establish.
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 practitioner preparing for the 200-901 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Infrastructure and Automation — This question tests Infrastructure and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Serial0/0/0 — The output shows that Serial0/0/0 is in the 'down/down' state, which indicates a Layer 1 or Layer 2 issue. Since the serial interface is administratively up (not 'administratively down'), the 'down/down' status points to a Layer 2 problem, such as a missing keepalive, encapsulation mismatch, or loss of carrier detect (CD) signal, rather than a Layer 3 addressing or routing issue.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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