The correct command is show log messages | last 50. This works because the pipe to the last filter in Junos CLI instructs the system to display only the final N lines of the output, and when combined with the show log messages command—which reads the /var/log/messages file—it efficiently retrieves the most recent 50 entries. On the JNCIA-Junos exam, this tests your understanding of operational mode commands and CLI filters, often appearing as a straightforward question where a common trap is confusing last with the match or count filter. Remember that last is specifically for tailing output, not for searching or counting lines. A helpful memory tip: think of the last command as the “tail” of the log—just as you’d look at the last page of a book for the newest information, you use last to grab the most recent log messages.
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.
A technician needs to view the last 50 log messages from the system log file. Which command accomplishes this?
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.
Why wrong: This is not a valid command. The correct command is 'show log messages' with optional filters.
B
monitor start messages
Why wrong: 'monitor start messages' displays log messages in real-time as they are generated. It does not show historical messages.
C
show system syslog
Why wrong: 'show system syslog' shows the syslog configuration, not the actual log messages. It displays what is being logged and where.
D
show log messages | last 50
The 'show log messages' command displays log entries from the messages file, and piping with '| last 50' shows the last 50 lines. This is the proper way to view recent log messages.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
show log messages | last 50
Option D is correct because the 'show log messages | last 50' command displays the last 50 lines from the /var/log/messages file on a Junos device. The pipe to 'last' is a Junos CLI filter that outputs only the final N lines of the command output, which is exactly what is needed to view the most recent log entries.
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 system log messages
Why it's wrong here
This is not a valid command. The correct command is 'show log messages' with optional filters.
✗
monitor start messages
Why it's wrong here
'monitor start messages' displays log messages in real-time as they are generated. It does not show historical messages.
✗
show system syslog
Why it's wrong here
'show system syslog' shows the syslog configuration, not the actual log messages. It displays what is being logged and where.
✓
show log messages | last 50
Why this is correct
The 'show log messages' command displays log entries from the messages file, and piping with '| last 50' shows the last 50 lines. This is the proper way to view recent log messages.
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
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the 'show log' command with 'show system syslog' or 'show system log messages', misremembering the exact syntax for viewing log file contents versus configuration.
Trap categories for this question
Command / output trap
This is not a valid command. The correct command is 'show log messages' with optional filters.
Detailed technical explanation
How to think about this question
The 'show log' command reads from files in /var/log/, and the '| last' filter is a CLI pipe that uses a line-count buffer to output only the final N lines. In a real-world scenario, when troubleshooting a transient issue, using 'show log messages | last 50' is efficient because it avoids scrolling through thousands of older entries, and the output can be further filtered with 'match' to isolate specific events.
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 log messages | last 50 — Option D is correct because the 'show log messages | last 50' command displays the last 50 lines from the /var/log/messages file on a Junos device. The pipe to 'last' is a Junos CLI filter that outputs only the final N lines of the command output, which is exactly what is needed to view the most recent log entries.
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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