This JNCIA-JUNOS practice question tests your understanding of user interfaces. 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 network engineer wants to view the OSPF log entries in real time. They type 'show log messages | match ospf' and get output, but it does not update. What should they do to see real-time updates of OSPF log entries?
Use 'monitor start messages | match ospf'
This command monitors the messages file in real time and filters for OSPF entries.
Use 'show log messages | tail'
Why wrong: This shows the last lines, but does not update in real time.
Use 'monitor traffic interface ge-0/0/0'
Why wrong: This captures packets, not log entries.
Use 'request system syslog'
Why wrong: This is not a valid command for viewing logs in real time.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use 'monitor start messages | match ospf'
Option A is correct because the 'monitor start messages' command in Junos OS enables real-time streaming of syslog messages to the terminal, similar to 'tail -f' on a log file. Piping the output through '| match ospf' filters the live feed to show only OSPF-related entries. In contrast, 'show log messages' is a one-time snapshot that does not update automatically.
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.
Use 'monitor start messages | match ospf'
Why this is correct
This command monitors the messages file in real time and filters for OSPF entries.
Related concept
Read the scenario before looking for a memorised answer.
Use 'show log messages | tail'
Why it's wrong here
This shows the last lines, but does not update in real time.
Use 'monitor traffic interface ge-0/0/0'
Why it's wrong here
This captures packets, not log entries.
Use 'request system syslog'
Why it's wrong here
This is not a valid command for viewing logs in real time.
Common exam traps
The trap here is that candidates familiar with Cisco IOS may confuse 'show log' (which in Cisco can be used with 'monitor' for real-time output) with Junos 'show log', which is static, and overlook the Junos-specific 'monitor start' command for live log streaming.
Trap categories for this question
Command / output trap
This shows the last lines, but does not update in real time.
Detailed technical explanation
The 'monitor start' command in Junos OS uses a background process that continuously reads the specified file (e.g., /var/log/messages) and outputs new lines as they are written, analogous to 'tail -f' on Unix. The pipe to 'match' applies a regular expression filter in real time, allowing the engineer to see only OSPF-related syslog entries without overwhelming the terminal. This is particularly useful during OSPF adjacency troubleshooting, where you need to see neighbor state changes as they occur.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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FAQ
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
The correct answer is: Use 'monitor start messages | match ospf' — Option A is correct because the 'monitor start messages' command in Junos OS enables real-time streaming of syslog messages to the terminal, similar to 'tail -f' on a log file. Piping the output through '| match ospf' filters the live feed to show only OSPF-related entries. In contrast, 'show log messages' is a one-time snapshot that does not update automatically.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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