Quick Answer
The answer is the `show system uptime` command. This is the correct choice because it is the dedicated operational mode command in Junos OS that retrieves the exact time elapsed since the last system boot, alongside the current system time and the uptime of the routing protocol process (rpd). On the JNCIA-Junos exam, this question tests your familiarity with fundamental Junos operational commands for monitoring device health and stability. A common trap is confusing this with `show system information` or `show version`, which provide hardware and software details but not the specific boot duration metric. To remember this, think of the command as asking the device directly, “How long have you been awake?”—the word “uptime” is literally in the command name, making it the most intuitive choice for checking system uptime.
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 engineer needs to check the current system uptime on a Juniper device running Junos OS. Which command should they use?
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 system status
Why wrong: Not a valid Junos command for uptime.
show system health
Why wrong: Not a standard command; 'show system health' does not exist.
show system resources
Why wrong: Shows resource usage, not uptime.
show system uptime
Correct command to view system uptime.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
show system uptime
The correct command to check current system uptime on a Juniper device running Junos OS is 'show system uptime'. This command displays the time since the system was last booted, as well as the current time and the time since the routing protocol process (rpd) started. It is the standard operational command for this specific metric.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
show system status
Why it's wrong here
Not a valid Junos command for uptime.
show system health
Why it's wrong here
Not a standard command; 'show system health' does not exist.
show system resources
Why it's wrong here
Shows resource usage, not uptime.
show system uptime
Why this is correct
Correct command to view system uptime.
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.
Common exam traps
The trap here is that candidates may confuse 'show system uptime' with similar-sounding commands from other vendors (like Cisco's 'show version' or 'show system status'), leading them to select a non-existent or incorrect Junos command.
Trap categories for this question
Command / output trap
Not a valid Junos command for uptime.
Detailed technical explanation
The 'show system uptime' command retrieves the system uptime from the kernel's timekeeping subsystem, which tracks the time elapsed since the last boot. This is critical for verifying system stability after maintenance windows or unexpected reboots. In real-world scenarios, comparing the uptime of the routing engine (RE) with the uptime of the Packet Forwarding Engine (PFE) can help diagnose issues like RE switchovers or FPC restarts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
The correct answer is: show system uptime — The correct command to check current system uptime on a Juniper device running Junos OS is 'show system uptime'. This command displays the time since the system was last booted, as well as the current time and the time since the routing protocol process (rpd) started. It is the standard operational command for this specific metric.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the JNCIA-JUNOS exam.
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