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Junos OS Fundamentals practice questions

Use this page to practise Junos OS Fundamentals questions for this certification. Focus on how the exam tests junos os fundamentals in scenario format — understanding the why behind each answer builds more durable knowledge than memorising options.

Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.

Reviewed byJohnson Ajibi· MSc IT Security
20 questionsDomain: Junos OS Fundamentals
Practice 10 questionsBrowse domain →

What the exam tests

What to know about Junos OS Fundamentals

Junos OS Fundamentals questions on this certification test your ability to deploy and manage junos os fundamentals concepts in scenario-based situations.

Core Junos OS Fundamentals concepts and how they apply in real-world cloud scenarios.

How to deploy junos os fundamentals correctly and verify the outcome.

Troubleshooting junos os fundamentals issues by interpreting error output and system state.

Cloud best practices and Junos OS Fundamentals design trade-offs tested by this certification.

Watch out for

Common Junos OS Fundamentals exam traps

  • ▸Selecting the most expensive service when a simpler managed option meets the requirement.
  • ▸Forgetting that cloud resources must be explicitly secured — defaults are rarely secure.
  • ▸Choosing a global service fix when the issue is region-specific.
  • ▸Overlooking cost implications of cross-region data transfer in architecture questions.

Practice set

Junos OS Fundamentals questions

20 questions · select your answer, then reveal the explanation

Question 1mediummultiple choice
Read the full Junos OS Fundamentals explanation →

A 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?

Question 2easymultiple choice
Read the full Junos OS Fundamentals explanation →

An administrator needs to quickly revert all uncommitted configuration changes and return the device to the last committed configuration. Which command accomplishes this?

Question 3hardmultiple choice
Open the full BGP breakdown →

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?

Question 4mediummultiple choice
Read the full NAT/PAT explanation →

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?

Question 5easymultiple choice
Read the full Junos OS Fundamentals explanation →

An engineer needs to view the current active configuration on a Juniper device. Which command will display the configuration that is currently running?

Question 6mediummultiple choice
Read the full Junos OS Fundamentals explanation →

A network administrator is configuring a new interface and wants to ensure that the interface is enabled and can pass traffic. Which configuration element is required?

Question 7hardmultiple choice
Read the full Junos OS Fundamentals explanation →

During a maintenance window, an engineer needs to apply a series of configuration changes that are stored in a text file. Which command sequence should be used to load and apply the changes from the file?

Question 8easymultiple choice
Read the full Junos OS Fundamentals explanation →

An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?

Question 9mediummulti select
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Which TWO statements are true about the Junos OS candidate configuration model? (Choose two.)

Question 10hardmulti select
Read the full Junos OS Fundamentals explanation →

Which THREE commands are valid Junos operational mode commands for monitoring network diagnostics? (Choose three.)

Question 11easymulti select
Read the full Junos OS Fundamentals explanation →

Which TWO statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)

Question 12mediummultiple choice
Read the full Junos OS Fundamentals explanation →

Based on the exhibit, what is the most likely reason for the ping failure?

Exhibit

Refer to the exhibit.

user@router> show configuration interfaces ge-0/0/0
unit 0 {
    family inet {
        address 10.0.0.1/30;
    }
}

user@router> show interfaces terse ge-0/0/0
Interface               Admin Link Proto    Local                 Remote
ge-0/0/0                up    up   inet     10.0.0.1/30

user@router> ping 10.0.0.2 count 1
PING 10.0.0.2 (10.0.0.2): 56 data bytes
^C
--- 10.0.0.2 ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss
Question 13hardmultiple choice
Review the full routing breakdown →

Based on the exhibit, what is the most likely impact on the router?

Exhibit

Refer to the exhibit.

user@router> show log messages | match "kernel"
Jan 10 10:00:00 router kernel: pid 1234 (rpd), uid 0, was killed: out of swap space
Jan 10 10:00:01 router kernel: pid 1235 (rpd), uid 0, was killed: out of swap space
Question 14hardmultiple choice
Open the full BGP breakdown →

You are a network engineer at a service provider. You have a Juniper MX router that serves as a BGP route reflector for a large number of customer routes. Recently, the router has been experiencing high CPU utilization, and the BGP process (rpd) is consuming excessive memory. You suspect that the router is receiving too many routes from a specific BGP peer, causing the routing table to grow beyond the available memory. You need to diagnose the issue without affecting production traffic. Which course of action should you take?

Question 15mediummultiple choice
Read the full DNS explanation →

You are a network administrator for a large enterprise. You have a Juniper SRX firewall that is used as the primary internet gateway. Users are reporting that they are unable to access certain external websites. You check the device and find that the security policies appear correct, and the routing is in place. You suspect that the issue might be related to the DNS resolution. You want to verify that the device can resolve DNS names and that the DNS server configuration is correct. Which command should you use to test DNS resolution from the Juniper device?

Question 16mediummultiple choice
Review the full subnetting walkthrough →

A network engineer notices that a Junos device is not forwarding traffic for a specific subnet. The routing table shows the route for that subnet, but traffic is still not being forwarded. Which command should the engineer use to verify whether the firewall filter is dropping the traffic?

Question 17hardmulti select
Read the full Junos OS Fundamentals explanation →

Which THREE of the following statements are true regarding Junos OS commit operations?

Question 18easymultiple choice
Review the full routing breakdown →

Refer to the exhibit. An engineer wants to verify that static routes for 10.0.1.0/24 and 10.0.2.0/24 are present in the routing table. Based on the output, which statement is true?

Exhibit

Refer to the exhibit.
```
user@router> show route protocol static

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.0.1.0/24     *[Static/5] 00:10:00, metric 0
                    > to 192.168.1.1 via ge-0/0/0.0
10.0.2.0/24     *[Static/5] 00:10:00, metric 0
                    > to 192.168.1.2 via ge-0/0/0.0
192.168.1.0/24  *[Direct/0] 00:15:00, metric 0
                    > via ge-0/0/0.0
```
Question 19hardmultiple choice
Open the full BGP breakdown →

You are administering a Juniper MX240 router that provides connectivity to multiple customer sites. The router uses BGP to exchange routes with two upstream ISPs. Recently, you applied a new firewall filter to the loopback interface to restrict management access. After committing the configuration, you can no longer establish SSH sessions to the router from the management network. You are currently connected via console. The loopback filter is still applied. You suspect the filter is blocking SSH traffic from the management network. What should you do to restore SSH access without losing the other filter rules?

Question 20easymultiple choice
Read the full Junos OS Fundamentals explanation →

A network engineer needs to check the operational status of all interfaces on a Juniper device. Which command provides a summary of interface status including link state, protocol state, and error counters?

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Frequently asked questions

What does the JNCIA-JUNOS exam test about Junos OS Fundamentals?
Junos OS Fundamentals questions on this certification test your ability to deploy and manage junos os fundamentals concepts in scenario-based situations.
How should I use these practice questions?
Select your answer before revealing the explanation. Then read why each option is right or wrong — this active recall approach builds retention far faster than re-reading notes.
Can I practise just Junos OS Fundamentals questions in a focused session?
Yes — the session launcher on this page draws every question from the Junos OS Fundamentals domain. Use a 10-question session first to gauge your baseline, then move to 20 or 30 once the weak spots are clear.
Where can I practise other JNCIA-JUNOS topics?
Use the topic links above to move to related areas, or go back to the JNCIA-JUNOS question bank to see all topics.
Are these real exam questions or dumps?
These are original practice questions written to test the same concepts the JNCIA-JUNOS exam covers. They are not copied from any real exam or dump site.