JN0-106 Operational Monitoring and Maintenance Practice Question
A network administrator is troubleshooting high CPU usage on a Juniper router. Which command helps identify which process is consuming the most CPU?
⚠ Common exam trap
Watch out — candidates often confuse 'show system processes extensive' with 'show system memory' or 'show log messages', mistakenly thinking memory or log analysis will reveal CPU hogs, when only the process list provides per-process CPU metrics.
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 system processes extensive
The 'show system processes extensive' command displays detailed information about all running processes, including CPU utilization, memory usage, and process IDs. This allows the administrator to identify which process (e.g., routing protocol daemon, management daemon) is consuming the most CPU cycles, directly addressing the troubleshooting need.
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 log messages
Why it's wrong here
The `show log messages` command retrieves messages written to the syslog buffer or a log file, such as interface events, user logins, or protocol errors. While a CPU spike might eventually be reflected in log entries, the command does not provide a real-time or per-process metric of CPU usage; it is asynchronous and historically framed. Even if high CPU were recorded in some log, you would not see which process consumed the cycles without inspecting process tables.
- ✗
show system memory
Why it's wrong here
The `show system memory` command reports memory utilization on the Routing Engine, including buffer pool usage, free memory, and a summary of allocated kernel and user memory. It does not expose the CPU load percentage, per-process CPU time, or scheduler state; a process that hogs CPU can do so with minimal memory footprint. This command is meant for diagnosing memory exhaustion or leaks, not for identifying the cause of high CPU utilization.
- ✓
show system processes extensive
Why this is correct
The `show system processes extensive` command is the correct diagnostic tool because it provides a detailed snapshot of every running process on the Junos device, including their IDs, CPU utilization percentages, and the cumulative time spent in user and system mode. The `extensive` keyword adds thread-level details and memory usage, enabling an administrator to pinpoint exactly which process is driving the high CPU load, such as rpd or mgd. This directly addresses the troubleshooting scenario.
- ✗
show interfaces
Why it's wrong here
The `show interfaces` command displays per-interface operational statistics like input/output packet counts, error rates, and traffic bandwidth utilization. While extremely high interface traffic might contribute to overall CPU load due to interrupt handling or protocol queue processing, it does not show the internal CPU usage of the Routing Engine or enumerate processes. It is a command for link-level performance analysis, not for isolating which software component is consuming CPU cycles.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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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.