20+ practice questions focused on Junos OS Fundamentals — one of the most tested topics on the Juniper Networks Certified Associate Junos JNCIA-Junos exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Junos OS Fundamentals PracticeA network engineer is configuring a new Juniper device and needs to ensure that the configuration is saved persistently across reboots. Which command should be used?
Explanation: The `commit` command activates the candidate configuration and saves it to the active configuration database, ensuring it persists across reboots. Without a commit, any changes made in candidate mode are lost when the device restarts.
An administrator needs to quickly revert all uncommitted configuration changes and return the device to the last committed configuration. Which command accomplishes this?
Explanation: The command 'rollback 0' reverts all uncommitted configuration changes and returns the device to the last committed configuration. In Junos, the rollback command uses a numeric argument to specify which previous configuration to load, with 0 always referring to the most recently committed configuration. This effectively discards any pending changes in the candidate configuration without requiring a commit.
A Juniper device is experiencing high CPU utilization due to a routing protocol process. The engineer suspects a specific BGP peer is causing the issue. Which operational command can be used to collect diagnostic information about the routing protocol processes?
Explanation: Option A is correct because 'show system processes extensive' displays detailed CPU and memory usage for each individual process, including routing protocol daemons like bgpd. This allows the engineer to identify which specific BGP peer or process is consuming excessive CPU resources, rather than just seeing aggregate routing protocol statistics.
A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?
Explanation: Option C is correct because the 'traceroute' command in Junos is specifically designed to trace the path packets take to a remote destination by sending UDP probes with increasing TTL values and analyzing ICMP Time Exceeded messages from intermediate routers. This directly addresses the junior engineer's need to map the Layer 3 path and identify where connectivity failures occur.
An engineer needs to view the current active configuration on a Juniper device. Which command will display the configuration that is currently running?
Explanation: The 'show configuration' command displays the current active configuration that is committed and running on a Juniper device. Unlike Cisco's 'show running-config', Junos uses a commit model where the candidate configuration is activated only after a 'commit' operation, and 'show configuration' shows that committed, active configuration.
+15 more Junos OS Fundamentals questions available
Practice all Junos OS Fundamentals questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Junos OS Fundamentals. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Junos OS Fundamentals questions on the JNCIA-JUNOS frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Junos OS Fundamentals is tested as part of the Juniper Networks Certified Associate Junos JNCIA-Junos blueprint. Practicing with targeted Junos OS Fundamentals questions ensures you can handle any format or difficulty that appears.
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Difficulty is subjective, but Junos OS Fundamentals is a high-priority exam concept tested in multiple ways — direct recall, scenario analysis, and command-output interpretation. Consistent practice is the best way to build confidence.
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