The answer is the `show chassis environment` command, which is the correct choice because it provides real-time sensor readings for temperature, voltage, and fan status on Juniper devices. This command directly fulfills the operator’s need to monitor chassis temperature and voltage sensors by polling the hardware monitoring subsystem and displaying the current state of all environmental components. On the JNCIA-Junos exam, this question tests your knowledge of operational monitoring commands under the “Chassis and Hardware” topic, often appearing as a straightforward recall item where a common trap is confusing it with `show chassis hardware` (which lists components and serial numbers, not sensor readings). A reliable memory tip is to think of “environment” as the physical conditions around the hardware—temperature, voltage, and fans—so when you need to check the health of the chassis environment, that command is your go-to.
JNCIA-JUNOS Operational Monitoring and Maintenance Practice Question
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
An operator wants to monitor the temperature and voltage sensors on a Juniper chassis. Which command displays current sensor readings?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
'show chassis environment' displays temperature, voltage, and fan status for the chassis components. It is the standard command for environmental monitoring.
B
show chassis hardware
Why wrong: 'show chassis hardware' shows inventory of hardware components (serial numbers, part numbers, etc.), not current sensor readings.
C
show system health
Why wrong: 'show system health' is not a valid Junos command. The correct command is 'show chassis environment'.
D
show log messages | match temperature
Why wrong: Log messages may contain temperature warnings, but they do not provide a live, structured view of all sensors. 'show chassis environment' is the proper command.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
show chassis environment
The 'show chassis environment' command displays real-time sensor readings for temperature, voltage, and fan status on Juniper devices. It is the standard operational command for monitoring chassis environmental health, directly matching the operator's requirement to check temperature and voltage sensors.
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.
✓
show chassis environment
Why this is correct
'show chassis environment' displays temperature, voltage, and fan status for the chassis components. It is the standard command for environmental monitoring.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
show chassis hardware
Why it's wrong here
'show chassis hardware' shows inventory of hardware components (serial numbers, part numbers, etc.), not current sensor readings.
✗
show system health
Why it's wrong here
'show system health' is not a valid Junos command. The correct command is 'show chassis environment'.
✗
show log messages | match temperature
Why it's wrong here
Log messages may contain temperature warnings, but they do not provide a live, structured view of all sensors. 'show chassis environment' is the proper command.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'show chassis hardware' (static inventory) with 'show chassis environment' (dynamic sensor data), or assume 'show system health' is a valid Junos command when it is not.
Trap categories for this question
Command / output trap
'show chassis hardware' shows inventory of hardware components (serial numbers, part numbers, etc.), not current sensor readings.
Detailed technical explanation
How to think about this question
The 'show chassis environment' command queries the chassis management controller (CMC) or Routing Engine (RE) sensors via the I2C bus, providing real-time values for temperature (in Celsius), voltage (in volts), and fan RPM. In production, this command is critical for proactive monitoring; for example, if a fan fails, the output shows 'Failed' status, and temperature thresholds (e.g., 65°C for normal, 80°C for alarm) trigger alerts to prevent hardware damage.
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 JNCIA-JUNOS 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.
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: show chassis environment — The 'show chassis environment' command displays real-time sensor readings for temperature, voltage, and fan status on Juniper devices. It is the standard operational command for monitoring chassis environmental health, directly matching the operator's requirement to check temperature and voltage sensors.
What should I do if I get this JNCIA-JUNOS 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: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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