Show Log Messages with Match — Filtering Syslog | JNCIA-Junos Explained
This JNCIA-JUNOS practice question tests your understanding of user interfaces. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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
user@router> help syslog messages | match error
KERNEL_ERROR Kernel error messages
USER_ERROR User-level error messages
DAEMON_ERROR Daemon error messages
Refer to the exhibit. What does this command accomplish?
Exhibit
user@router> help syslog messages | match error
KERNEL_ERROR Kernel error messages
USER_ERROR User-level error messages
DAEMON_ERROR Daemon error messages
A
Displays help for syslog messages that include 'error'.
Why wrong: This option incorrectly describes the command as displaying help. The command displays actual log messages, not help.
B
Displays all syslog messages.
Why wrong: This option is incorrect because the command filters the output to only lines containing 'error', not all messages.
C
Displays syslog messages containing the word 'error'.
This is correct because the command filters the system log for lines containing the substring 'error'.
D
Displays the error log file.
Why wrong: This option is incorrect because there is no dedicated error log file; the command filters the standard messages log.
The answer is that the command displays help for syslog messages that include 'error'. This is accomplished by using the pipe (|) with the match filter, which acts as a grep-like function in the Junos CLI, scanning the output of 'show log messages' and returning only lines containing the string 'error'. On the JNCIA-Junos exam, this tests your understanding of operational mode filtering and the specific behavior of the 'show log messages' command, which is a core syslog viewing tool. A common trap is assuming the match filter performs a whole-word search or that it modifies the log file itself—it does not; it simply filters the displayed output. Remember the memory tip: "Match is a magnifying glass, not a scalpel"—it highlights relevant lines without altering the underlying log data.
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
✓
Displays syslog messages containing the word 'error'.
The command shown filters the output of the system log file to display only lines containing the substring 'error'. This allows the administrator to quickly see log entries related to errors, rather than viewing all messages or a dedicated error log file.
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.
✗
Displays help for syslog messages that include 'error'.
Why it's wrong here
This option incorrectly describes the command as displaying help. The command displays actual log messages, not help.
✗
Displays all syslog messages.
Why it's wrong here
This option is incorrect because the command filters the output to only lines containing 'error', not all messages.
✓
Displays syslog messages containing the word 'error'.
Why this is correct
This is correct because the command filters the system log for lines containing the substring 'error'.
Related concept
Read the scenario before looking for a memorised answer.
✗
Displays the error log file.
Why it's wrong here
This option is incorrect because there is no dedicated error log file; the command filters the standard messages log.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often assume that the 'match' operator performs a whole-word search or that there is a dedicated error log file, but in Junos it performs a substring match on the default messages log.
Trap categories for this question
Command / output trap
This option incorrectly describes the command as displaying help. The command displays actual log messages, not help.
Detailed technical explanation
How to think about this question
In Junos, the 'show log' command reads the /var/log/messages file by default, and the pipe to 'match' uses a regular expression (grep) to filter lines. The 'match' operator is case-sensitive by default and matches any occurrence of the string, not whole words. This is useful for quickly isolating specific events in a large log file, such as when troubleshooting interface flaps or routing protocol errors, where searching for 'error' can reveal critical syslog entries without needing to parse the entire log.
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.
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Displays syslog messages containing the word 'error'. — The command shown filters the output of the system log file to display only lines containing the substring 'error'. This allows the administrator to quickly see log entries related to errors, rather than viewing all messages or a dedicated error log file.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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