- A
A firewall filter was applied to the management interface that blocks all traffic
Why wrong: A filter could block traffic, but the question indicates the management interface is in a dedicated routing instance, and filters are less likely to be accidentally applied without noticing.
- B
NTP was configured with an incorrect server address
Why wrong: NTP misconfiguration does not impact connectivity; it only affects time synchronization.
- C
A syslog server was configured that is unreachable
Why wrong: Syslog does not affect connectivity; it is a logging protocol.
- D
The routing instance for the management interface was accidentally removed
If the management interface's routing instance is removed, the interface loses its route to the management network, causing connectivity loss.
JNCIA-JUNOS Junos OS Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 notices that after committing a configuration change on a Juniper MX router, the device loses connectivity to the management network. The management interface is part of a dedicated management routing instance. Which of the following is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The routing instance for the management interface was accidentally removed
The management interface is part of a dedicated management routing instance (often named mgmt_junos). If this routing instance is accidentally removed during a commit, the management interface loses its routing context and becomes unreachable, causing loss of connectivity to the management network. This is a common misconfiguration when an administrator modifies routing instance configurations without realizing the management interface depends on it.
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.
- ✗
A firewall filter was applied to the management interface that blocks all traffic
Why it's wrong here
A filter could block traffic, but the question indicates the management interface is in a dedicated routing instance, and filters are less likely to be accidentally applied without noticing.
- ✗
NTP was configured with an incorrect server address
Why it's wrong here
NTP misconfiguration does not impact connectivity; it only affects time synchronization.
- ✗
A syslog server was configured that is unreachable
Why it's wrong here
Syslog does not affect connectivity; it is a logging protocol.
- ✓
The routing instance for the management interface was accidentally removed
Why this is correct
If the management interface's routing instance is removed, the interface loses its route to the management network, causing connectivity loss.
Clue confirmation
The clue word "most likely" 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 often assume a firewall filter or service configuration (like NTP or syslog) is the cause, but the real issue is the removal of the routing instance that provides the logical separation for the management interface.
Detailed technical explanation
How to think about this question
In Junos, a management routing instance (e.g., mgmt_junos) isolates the management interface (e.g., fxp0 or em0) from the default routing table. When this routing instance is removed, the interface falls back to the default routing instance, which typically has no routes for the management subnet, causing unreachability. The commit operation validates syntax but does not prevent logical errors like removing a routing instance that is in use, which is why this mistake can slip through.
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?
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The routing instance for the management interface was accidentally removed — The management interface is part of a dedicated management routing instance (often named mgmt_junos). If this routing instance is accidentally removed during a commit, the management interface loses its routing context and becomes unreachable, causing loss of connectivity to the management network. This is a common misconfiguration when an administrator modifies routing instance configurations without realizing the management interface depends on it.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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