- A
monitor start messages | match "error"
Why wrong: This command is used for real-time monitoring of the messages log file. While it can filter for 'error', it is not efficient for checking existing log files as it continuously displays new messages.
- B
show log file messages | match "error"
Why wrong: This command is invalid in JUNOS. The correct syntax is 'show log messages', not 'show log file messages'. Therefore, it is not a valid command.
- C
show log messages
This is the correct command to display the contents of the /var/log/messages file. Although it lacks a match filter, it is the only valid option for viewing existing system log messages.
- D
show system syslog messages
Why wrong: This command is not valid in JUNOS. The correct command to view system log messages is 'show log messages' or 'show system messages', but not 'show system syslog messages'.
Filtering Log Files for Error Messages in Junos
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 administrator is asked to check the system log files for any error messages related to interface failures. Which command would be most efficient?
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.
Quick Answer
The answer is to use the command show log messages | match "error". This is the most efficient method because the show log messages command displays the contents of the primary system log file, /var/log/messages, and piping the output to the match filter isolates only those lines containing the keyword "error," allowing you to quickly pinpoint interface failure issues without sifting through irrelevant entries. On the JNCIA-Junos exam, this question tests your ability to efficiently navigate Junos operational mode and apply filters to system logs, a common task for troubleshooting. A frequent trap is using show log without a filter, which dumps the entire log and wastes time, or using a grep-like command incorrectly. Remember the memory tip: "Pipe to match for a catch" — always pair show log with match to zero in on specific error messages.
Answer choices
Why each option matters
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
Option C is correct because 'show log messages' is the standard JUNOS command to display the contents of the /var/log/messages file. While it does not include a filter, it is the only valid command among the options that allows the administrator to view existing system log messages. The other options are either invalid commands (B and D) or used for real-time monitoring (A), which is not efficient for checking historical log files.
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.
- ✗
monitor start messages | match "error"
Why it's wrong here
This command is used for real-time monitoring of the messages log file. While it can filter for 'error', it is not efficient for checking existing log files as it continuously displays new messages.
- ✗
show log file messages | match "error"
Why it's wrong here
This command is invalid in JUNOS. The correct syntax is 'show log messages', not 'show log file messages'. Therefore, it is not a valid command.
- ✓
show log messages
Why this is correct
This is the correct command to display the contents of the /var/log/messages file. Although it lacks a match filter, it is the only valid option for viewing existing system 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.
- ✗
show system syslog messages
Why it's wrong here
This command is not valid in JUNOS. The correct command to view system log messages is 'show log messages' or 'show system messages', but not 'show system syslog messages'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'monitor start messages' with 'show log messages', thinking the real-time monitor is more efficient for checking logs, but the question asks for checking existing log files, not monitoring live events.
Trap categories for this question
Command / output trap
This command is used for real-time monitoring of the messages log file. While it can filter for 'error', it is not efficient for checking existing log files as it continuously displays new messages.
Detailed technical explanation
How to think about this question
In JUNOS, system log files are stored in /var/log/ by default, with 'messages' being the primary log file for general system events, including interface state changes and errors. The 'show log <filename>' command reads the specified log file from disk, and when combined with 'match', it uses a grep-like pattern matching engine to filter lines, which is efficient because it only processes the file once and outputs matching lines. In a real-world scenario, an administrator troubleshooting recurring interface flapping would use 'show log messages | match "interface.*down"' to quickly isolate relevant events without scrolling through thousands of lines.
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.
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
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 — Option C is correct because 'show log messages' is the standard JUNOS command to display the contents of the /var/log/messages file. While it does not include a filter, it is the only valid command among the options that allows the administrator to view existing system log messages. The other options are either invalid commands (B and D) or used for real-time monitoring (A), which is not efficient for checking historical log files.
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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Last reviewed: Jun 24, 2026
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