JN0-106 Operational Monitoring and Maintenance Practice Question
A network operator needs to upgrade the Junos OS on the backup RE (re1) of a dual-RE system. Which procedure ensures that only the backup RE is upgraded and rebooted without affecting the forwarding plane?
⚠ Common exam trap
A common mix-up: candidates confuse the 'both' option with a safe upgrade method, not realizing it reboots both REs simultaneously and disrupts traffic, or they may incorrectly assume that copying the image manually and using a non-existent 'slice' command is a valid procedure.
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 'request system software add <image> re1' and then 'request system reboot re1'
The 'request system software add <image> re1' command installs the Junos OS image only on the backup Routing Engine (RE1), and the subsequent 'request system reboot re1' reboots only that RE. In a dual-RE system, this procedure isolates the upgrade to the backup RE, ensuring the forwarding plane remains active on the primary RE (RE0) and no traffic disruption occurs.
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 <image> re1' and then 'request system reboot re1'
Why this is correct
Targeting re1 with the 're1' keyword ensures the image is installed only on the backup Routing Engine, leaving the active primary RE untouched. Rebooting re1 restarts only that RE; the primary continues handling forwarding and control traffic, so there is no service interruption. After re1 returns online as standby, it is ready to assume primary role in a later switchover, which is the correct maintenance procedure.
- ✗
Use 'request system software add <image> both' and then 'request system reboot both'
Why it's wrong here
The 'both' keyword installs the image on both Routing Engines simultaneously, and then the reboot command restarts both REs at the same time. This eliminates the redundancy that protects the forwarding plane; if both REs go down, even with graceful Routing Engine switchover, all control and data plane activity is lost. The intended task specifically requires upgrading the backup RE alone, not forcing a full outage.
- ✗
Use 'request system software add <image> re0' and then 'request system reboot re0'
Why it's wrong here
Typically re0 is the primary Routing Engine in a dual-RE chassis, so issuing 'request system software add <image> re0' installs on the active RE. Rebooting re0 forces a switchover to re1, but unless graceful switchover (GRES) and nonstop routing are fully configured, this disrupts forwarding. Even if GRES is enabled, the operator's goal is to update the backup, not the active RE, and rebooting the primary is exactly what should be deferred.
- ✗
Copy the image to both REs and reboot the backup RE with 'request system reboot slice 1'
Why it's wrong here
Copying the image to both REs is unnecessary and can cause the primary to load a new image before the backup is ready, increasing risk. Furthermore, 'request system reboot slice 1' is not a valid Junos command; Routing Engines are addressed as re0 and re1, not slices. The correct approach is to use the 're1' argument on both the 'request system software add' and 'request system reboot' commands to limit the action to the backup.
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JA
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.