- A
Roll back to the previous configuration to ensure the device is in a known state.
Why wrong: Rolling back may remove the new policy and not address the root cause of ordering.
- B
Run 'show configuration | display set | match policy' to verify the policy is present.
Why wrong: This shows the candidate configuration but not the active order; it may not reveal if another policy intercepts the traffic.
- C
Run 'show security policies detail' and examine the policy order to see if a previous policy is denying the traffic.
This command displays all active security policies in sequence, helping identify ordering issues.
- D
Check the firewall logs with 'show log messages | match deny' to see which policy is denying.
Why wrong: Logs show denials but require interpretation; checking policy order is more direct.
JNCIA-JUNOS Junos Configuration Basics Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos configuration basics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Scenario: Your company has a Juniper SRX300 firewall used as a branch gateway. It runs Junos 15.1X49. The firewall has multiple security policies, NAT rules, and VPN tunnels. Recently, you added a new security policy to allow traffic from the internal network to a specific public server. After committing, you notice that the firewall is logging repeated denials for traffic that should be matched by the new policy. The policy appears correctly configured in the candidate configuration. You want to verify that the policy is actually active and check for any hidden rules that might be causing the issue. Which of the following is the most effective first step to troubleshoot this problem?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
Run 'show security policies detail' and examine the policy order to see if a previous policy is denying the traffic.
Option C is correct because the most common cause of traffic being denied despite a seemingly correct new policy is that a preceding policy in the security policy order matches the traffic and denies it before the new policy is evaluated. Junos security policies are evaluated in sequential order from top to bottom, and the first matching policy is applied. Running 'show security policies detail' displays the active policy order, including any hidden or default policies, allowing you to identify if a deny policy earlier in the list is intercepting the traffic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Roll back to the previous configuration to ensure the device is in a known state.
Why it's wrong here
Rolling back may remove the new policy and not address the root cause of ordering.
- ✗
Run 'show configuration | display set | match policy' to verify the policy is present.
Why it's wrong here
This shows the candidate configuration but not the active order; it may not reveal if another policy intercepts the traffic.
- ✓
Run 'show security policies detail' and examine the policy order to see if a previous policy is denying the traffic.
Why this is correct
This command displays all active security policies in sequence, helping identify ordering issues.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Check the firewall logs with 'show log messages | match deny' to see which policy is denying.
Why it's wrong here
Logs show denials but require interpretation; checking policy order is more direct.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a correctly configured policy will automatically be applied, but Junos requires careful attention to policy order, and the exam tests whether you know to verify the active policy sequence rather than just the configuration syntax.
Trap categories for this question
Command / output trap
This shows the candidate configuration but not the active order; it may not reveal if another policy intercepts the traffic.
Detailed technical explanation
How to think about this question
Junos security policies are evaluated in a strict sequential order based on their position in the 'security policies from-zone to-zone' hierarchy. When a new policy is added, it is typically inserted at the end of the policy list by default unless a specific insert command is used. A common subtle behavior is that a default or implicit deny-all policy at the end of the list will not cause this issue; instead, an explicit deny policy placed before the new allow policy will match first. In real-world scenarios, administrators often forget that policies are ordered and that a 'deny' policy with broad matching criteria (e.g., any/any) can silently block traffic intended for a more specific allow rule.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
Junos Configuration Basics — This question tests Junos Configuration Basics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run 'show security policies detail' and examine the policy order to see if a previous policy is denying the traffic. — Option C is correct because the most common cause of traffic being denied despite a seemingly correct new policy is that a preceding policy in the security policy order matches the traffic and denies it before the new policy is evaluated. Junos security policies are evaluated in sequential order from top to bottom, and the first matching policy is applied. Running 'show security policies detail' displays the active policy order, including any hidden or default policies, allowing you to identify if a deny policy earlier in the list is intercepting the traffic.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS 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 JNCIA-JUNOS exam.
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