JN0-106 Operational Monitoring and Maintenance Practice Question
An operator wants to monitor the temperature and voltage sensors on a Juniper chassis. Which command displays current sensor readings?
⚠ Common exam trap
Many exam-takers confuse 'show chassis hardware' (static inventory) with 'show chassis environment' (dynamic sensor data), or assume 'show system health' is a valid Junos command when it is not.
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
✓
show chassis environment
The 'show chassis environment' command displays real-time sensor readings for temperature, voltage, and fan status on Juniper devices. It is the standard operational command for monitoring chassis environmental health, directly matching the operator's requirement to check temperature and voltage sensors.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
show chassis environment
Why this is correct
The `show chassis environment` operational command in Junos is the standard tool for environmental monitoring: it reads live temperature sensors, voltage rails, and fan speeds across the Routing Engine, line cards, and power supplies. Without any filters it returns current values for all monitored components, and with `detail` it also shows acceptable operating ranges and alarm thresholds. This is the only option that delivers a structured, real-time view of the exact sensors the operator asked about.
- ✗
show chassis hardware
Why it's wrong here
The `show chassis hardware` command outputs inventory data such as model numbers, serial numbers, part numbers, and hardware revision information for installed FRUs, not runtime telemetry. While that command verifies what hardware is present or helps track spares, it never reads the environmental sensors. An operator inspecting temperature or voltage needs a command that polls the sensor plane, which is exactly what `show chassis environment` does.
- ✗
show system health
Why it's wrong here
`show system health` is not a recognized Junos operational command in standard Junos OS; typing it returns a syntax or unknown-command error. Some other network operating systems use that phrase, but Junos uses `show chassis environment` for sensor values. Because the command is not valid, it cannot produce any temperature or voltage readings, regardless of the operator's intent.
- ✗
show log messages | match temperature
Why it's wrong here
`show log messages | match temperature` pipes the system message log through a filter to find lines containing the string "temperature." This yields only historical log entries—usually alarms or threshold notices—that were previously written by the chassis daemon, not current live sensor values. If no temperature event has been logged recently, the output is empty even when a component is running warm, so this is neither a real-time nor a reliable way to monitor environmental conditions.
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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.