- A
Roll back to the previous configuration using 'rollback 0' and commit.
Why wrong: This reverts all changes, including any other desired modifications made after the last commit.
- B
Add a new term at the end of the filter that accepts SSH traffic from any source.
Why wrong: Adding at the end may not help if a preceding deny term matches the SSH traffic first.
- C
Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first.
This ensures SSH from the management network is accepted before any deny rules are evaluated.
- D
Delete the firewall filter from the loopback interface and commit.
Why wrong: This removes all filter rules, not just the blocking part, and may expose the router to other threats.
JNCIA-JUNOS Junos OS Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
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?
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
Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first.
Option C is correct because firewall filters in Junos are evaluated in order, and adding a term at the beginning that explicitly accepts SSH traffic from the management network ensures that the SSH packets are permitted before any subsequent deny terms are evaluated. This preserves all existing filter rules while restoring SSH access. The 'insert' command or reordering terms is necessary to place the new term first, as the default behavior appends new terms to the end of the filter.
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 using 'rollback 0' and commit.
Why it's wrong here
This reverts all changes, including any other desired modifications made after the last commit.
- ✗
Add a new term at the end of the filter that accepts SSH traffic from any source.
Why it's wrong here
Adding at the end may not help if a preceding deny term matches the SSH traffic first.
- ✓
Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first.
Why this is correct
This ensures SSH from the management network is accepted before any deny rules are evaluated.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Delete the firewall filter from the loopback interface and commit.
Why it's wrong here
This removes all filter rules, not just the blocking part, and may expose the router to other threats.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume adding a permit rule anywhere in the filter will work, but they forget that Junos filters are order-dependent and that new terms are appended to the end by default, which may be after a deny term that blocks the traffic.
Detailed technical explanation
How to think about this question
Junos firewall filters are evaluated top-down, with an implicit 'deny all' at the end if no explicit 'accept' is matched. The loopback interface (lo0) is a virtual interface that represents the router's control plane, so filters applied to it affect all traffic destined to the router itself, including management protocols like SSH. Using the 'insert' command (e.g., 'insert term permit-ssh before term deny-all') allows precise ordering without rewriting the entire filter.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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 OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first. — Option C is correct because firewall filters in Junos are evaluated in order, and adding a term at the beginning that explicitly accepts SSH traffic from the management network ensures that the SSH packets are permitted before any subsequent deny terms are evaluated. This preserves all existing filter rules while restoring SSH access. The 'insert' command or reordering terms is necessary to place the new term first, as the default behavior appends new terms to the end of the filter.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 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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