- A
firewall-cmd --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent
Why wrong: This rich rule is missing the zone; it will apply to the default zone but it's better practice to specify the zone explicitly.
- B
firewall-cmd --add-service=ssh --add-source=192.168.10.0/24 --zone=internal --permanent
Why wrong: This command combines --add-service and --add-source with a zone, but the correct way to restrict by source is with a rich rule.
- C
firewall-cmd --add-source=192.168.10.0/24 --add-service=ssh --permanent
Why wrong: This command adds a source-based rule but does not specify a zone; it may not work as intended because it applies to the default zone but without a rich rule.
- D
firewall-cmd --zone=public --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent
This is the correct syntax for adding a rich rule that allows SSH from a specific source in a specific zone.
LFCS Networking Practice Question
This LFCS practice question tests your understanding of networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A system administrator wants to allow incoming SSH connections from a specific IP range 192.168.10.0/24 using firewalld. Which command should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"which command"Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
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
firewall-cmd --zone=public --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent
Option D is correct because it explicitly targets the 'public' zone (the default zone for external-facing interfaces) and uses a rich rule to allow SSH traffic only from the 192.168.10.0/24 source IP range. The --permanent flag ensures the rule persists across reloads. This is the precise syntax required by firewalld for source-specific service access.
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.
- ✗
firewall-cmd --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent
Why it's wrong here
This rich rule is missing the zone; it will apply to the default zone but it's better practice to specify the zone explicitly.
- ✗
firewall-cmd --add-service=ssh --add-source=192.168.10.0/24 --zone=internal --permanent
Why it's wrong here
This command combines --add-service and --add-source with a zone, but the correct way to restrict by source is with a rich rule.
- ✗
firewall-cmd --add-source=192.168.10.0/24 --add-service=ssh --permanent
Why it's wrong here
This command adds a source-based rule but does not specify a zone; it may not work as intended because it applies to the default zone but without a rich rule.
- ✓
firewall-cmd --zone=public --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent
Why this is correct
This is the correct syntax for adding a rich rule that allows SSH from a specific source in a specific zone.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often forget to specify the zone (defaulting to the wrong zone) or incorrectly assume that --add-source and --add-service can be combined directly without a rich rule, leading to a rule that either applies to all sources or fails silently.
Trap categories for this question
Command / output trap
This command combines --add-service and --add-source with a zone, but the correct way to restrict by source is with a rich rule.
Detailed technical explanation
How to think about this question
Firewalld rich rules use the 'rule family' directive to specify IPv4 or IPv6, and the 'source address' attribute to define the allowed subnet. The 'service name' attribute maps to predefined service definitions in /usr/lib/firewalld/services/ (e.g., ssh.xml). The --permanent flag writes the rule to the zone's XML configuration, requiring a firewall-cmd --reload to take effect. In real-world scenarios, this granular control prevents SSH brute-force attacks from unauthorized subnets while allowing legitimate administrative access.
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 practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
- →
Networking — study guide chapter
Learn the concepts, then practise the questions
- →
Networking practice questions
Targeted practice on this topic area only
- →
All LFCS questions
513 questions across all exam domains
- →
Linux Foundation Certified System Administrator LFCS study guide
Full concept coverage aligned to exam objectives
- →
LFCS practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related LFCS practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
User and Group Management practice questions
Practise LFCS questions linked to User and Group Management.
Operation of Running Systems practice questions
Practise LFCS questions linked to Operation of Running Systems.
Essential Commands practice questions
Practise LFCS questions linked to Essential Commands.
Networking practice questions
Practise LFCS questions linked to Networking.
Service Configuration practice questions
Practise LFCS questions linked to Service Configuration.
Storage Management practice questions
Practise LFCS questions linked to Storage Management.
LFCS fundamentals practice questions
Practise LFCS questions linked to LFCS fundamentals.
LFCS scenario practice questions
Practise LFCS questions linked to LFCS scenario.
LFCS troubleshooting practice questions
Practise LFCS questions linked to LFCS troubleshooting.
Practice this exam
Start a free LFCS practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this LFCS question test?
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: firewall-cmd --zone=public --add-rich-rule='rule family="ipv4" source address="192.168.10.0/24" service name="ssh" accept' --permanent — Option D is correct because it explicitly targets the 'public' zone (the default zone for external-facing interfaces) and uses a rich rule to allow SSH traffic only from the 192.168.10.0/24 source IP range. The --permanent flag ensures the rule persists across reloads. This is the precise syntax required by firewalld for source-specific service access.
What should I do if I get this LFCS 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: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More LFCS practice questions
- A system administrator needs to ensure the Apache httpd service starts automatically on system boot. Which command shoul…
- Which THREE of the following are valid methods to mount an NFS filesystem on a client?
- Refer to the exhibit. The administrator wants to create a RAID 1 array using /dev/sdb1 and /dev/sdc1. Which command shou…
- A system administrator needs to list all files in the current directory, including hidden files, in a long listing forma…
- A user wants to find all files in /var/log that have been modified within the last 2 days. Which command should they use…
- A user needs to view the contents of a compressed log file /var/log/syslog.gz without first decompressing it. Which comm…
Last reviewed: Jun 25, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.