- A
Use 'deactivate protocols ospf' to disable OSPF entirely and then manually re-enable pieces.
Why wrong: Deactivating all OSPF may stop routing completely, and piecemeal re-enablement is risky.
- B
Immediately delete the OSPF configuration sections that were changed and re-add the original settings manually.
Why wrong: Manual re-entry is error-prone and time-consuming, prolonging the outage.
- C
Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability.
Rollback to the previous commit (1) and commit confirmed provides quick restoration with safety.
- D
Perform a 'load factory-default' and 'commit' to reset the device to base settings, then reconfigure from backup.
Why wrong: Factory reset would wipe everything and require full reconfiguration, causing longer downtime.
Quick Answer
The correct answer is to use rollback 1 followed by commit confirmed 10. This works because rollback 1 reverts the active configuration to the last committed version—the stable OSPF setup before the problematic changes—while commit confirmed 10 applies that rollback with a ten-minute automatic confirmation timer. If the OSPF neighbor relationships stabilize and connectivity returns, the rollback becomes permanent; if the issue persists or you lose access, the router automatically reverts to the previous configuration, preventing a prolonged outage. On the JNCIA-Junos exam, this scenario tests your understanding of Junos configuration management and the commit confirmed feature, often appearing as a troubleshooting question where you must distinguish between rollback 0 (current active) and rollback 1 (previous commit). A common trap is to use commit confirmed alone without first rolling back, which would keep the problematic OSPF changes active. Memory tip: think “rollback first, then confirm” to avoid locking in a bad config.
JNCIA-JUNOS Junos Configuration Basics Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos configuration basics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Scenario: Your company has a Juniper MX Series router at a branch office running Junos 18.4. The device has been in production for two years with a stable configuration. Yesterday, a senior engineer made several changes to the OSPF configuration to optimize routing for a new link. They committed the changes and left for the day. This morning, the branch office experiences intermittent connectivity, and the OSPF neighbor relationships are flapping. You suspect the recent OSPF changes caused the issue. You have remote console access to the router. The goal is to restore network stability as quickly as possible while preserving the ability to re-apply the changes after troubleshooting. Which course of action should you take?
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
Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability.
Option C is correct because 'rollback 1' reverts the active configuration to the previous committed version (before the problematic OSPF changes), and 'commit confirmed 10' applies that rollback with a 10-minute confirmation timer. If connectivity stabilizes, the rollback becomes permanent; if not, the router automatically reverts to the previous configuration, ensuring no prolonged outage. This approach restores stability quickly while preserving the ability to later re-apply and test the OSPF changes in a controlled manner.
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.
- ✗
Use 'deactivate protocols ospf' to disable OSPF entirely and then manually re-enable pieces.
Why it's wrong here
Deactivating all OSPF may stop routing completely, and piecemeal re-enablement is risky.
- ✗
Immediately delete the OSPF configuration sections that were changed and re-add the original settings manually.
Why it's wrong here
Manual re-entry is error-prone and time-consuming, prolonging the outage.
- ✓
Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability.
Why this is correct
Rollback to the previous commit (1) and commit confirmed provides quick restoration with safety.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Perform a 'load factory-default' and 'commit' to reset the device to base settings, then reconfigure from backup.
Why it's wrong here
Factory reset would wipe everything and require full reconfiguration, causing longer downtime.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose Option A (deactivate OSPF) thinking it is a quick fix, but they overlook that deactivating the entire protocol causes a complete routing disruption, whereas 'rollback' with 'commit confirmed' is the precise, safe, and reversible method Junos provides for this exact scenario.
Detailed technical explanation
How to think about this question
Junos maintains a history of the last 50 committed configurations, accessible via 'rollback <N>', where N=0 is the current active configuration and N=1 is the previous commit. The 'commit confirmed' command activates a configuration with a timer (default 10 minutes); if the timer expires without a confirming 'commit', the system automatically performs a 'rollback 1' to the prior configuration, providing a safety net against misconfigurations that break connectivity. This mechanism is especially useful in OSPF scenarios where changes to timers (hello/dead intervals), area assignments, or interface costs can cause neighbor flapping.
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 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
Questions learners often ask
What does this JNCIA-JUNOS question test?
Junos Configuration Basics — This question tests Junos Configuration Basics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability. — Option C is correct because 'rollback 1' reverts the active configuration to the previous committed version (before the problematic OSPF changes), and 'commit confirmed 10' applies that rollback with a 10-minute confirmation timer. If connectivity stabilizes, the rollback becomes permanent; if not, the router automatically reverts to the previous configuration, ensuring no prolonged outage. This approach restores stability quickly while preserving the ability to later re-apply and test the OSPF changes in a controlled manner.
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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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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