JN0-106 Junos OS Fundamentals Practice Question
A technician needs to upgrade the Junos OS on a device that is part of a redundant cluster. Which approach minimizes traffic disruption?
⚠ Common exam trap
The trap here is that candidates might think simultaneous upgrades are efficient or that 'commit synchronize' is related to software upgrades, but Junos requires sequential node upgrades in a cluster to maintain redundancy and avoid traffic loss.
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
✓
Upgrade one node at a time, ensuring the cluster remains redundant.
Upgrading one node at a time in a redundant cluster ensures that at least one node remains active to handle traffic while the other is being upgraded. This approach maintains cluster redundancy and minimizes traffic disruption, as the active node continues forwarding traffic using the gratuitous ARP or VRRP mechanisms, and the upgraded node rejoins the cluster after reboot.
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 'request system software add' on both nodes at the same time.
Why it's wrong here
Issuing 'request system software add' on both nodes concurrently is a mistake because each node queues its own reboot after the software is committed. In a chassis cluster, both control planes would restart at the same time, breaking the active/standby redundancy and causing a full traffic outage. Even if you stagger the command, the dependency on the reboot flag makes simultaneous execution risky, so the cluster cannot fail over cleanly.
- ✗
Upgrade both nodes simultaneously to reduce maintenance time.
Why it's wrong here
Upgrading both nodes simultaneously to shorten the maintenance window defeats the purpose of a high-availability cluster. Since each node must reboot to load the new Junos OS, both would be unavailable at once, and the cluster would lose its redundant data-plane forwarding capability. Any traffic handled by the cluster would be dropped, not just briefly but for the entire reboot duration, which is unacceptable for production networks.
- ✓
Upgrade one node at a time, ensuring the cluster remains redundant.
Why this is correct
The correct method is to upgrade one node at a time: add the software to the backup node, let it reboot and rejoin the cluster as the new primary, then fail over and upgrade the old primary. This ensures that at least one node stays active throughout the process, preserving traffic forwarding and maintaining cluster redundancy. You can verify the cluster status with 'show chassis cluster status' before and after each node's reboot.
- ✗
Use the 'commit synchronize' command to keep configurations in sync after upgrade.
Why it's wrong here
'commit synchronize' is used to copy the active node's configuration to the backup node and keep the Junos configuration consistent across the cluster. It has no effect on the OS software version or the upgrade process itself. Running it after an upgrade only ensures configuration parity, not the successful loading of the new Junos image, so it cannot replace the sequential node upgrade procedure.
About these practice questions
Courseiva writes every JN0-106 question from scratch — 326 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This JN0-106 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 JN0-106 exam.