- A
firewall-cmd --zone=external --add-service=ssh --permanent
Why wrong: This opens SSH to all sources.
- B
firewall-cmd --zone=external --add-port=2222/tcp --permanent
Why wrong: This opens port 2222 to all sources.
- C
firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" service name="ssh" accept' --permanent
Why wrong: This allows SSH on port 22, not 2222.
- D
firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" port port="2222" protocol="tcp" accept' --permanent
This restricts SSH to port 2222 from the specified subnet.
Question 533 of 537
Using Firewalld Rich Rules to Allow SSH on a Custom Port
This EX200 practice question tests your understanding of manage security. 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 company requires that SSH access from the external network (10.0.1.0/24) only be allowed to port 2222, and all other incoming traffic on the firewall should be dropped. Which firewalld rule should be applied to the external zone?
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=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" port port="2222" protocol="tcp" accept' --permanent
Option D is correct because it uses a rich rule to explicitly allow incoming TCP traffic on port 2222 from the 10.0.1.0/24 source network, which matches the requirement. The default target for the external zone is 'drop', so only explicitly permitted traffic is allowed; this rule ensures SSH on port 2222 is accepted while all other incoming traffic is dropped.
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 --zone=external --add-service=ssh --permanent
Why it's wrong here
This opens SSH to all sources.
- ✗
firewall-cmd --zone=external --add-port=2222/tcp --permanent
Why it's wrong here
This opens port 2222 to all sources.
- ✗
firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" service name="ssh" accept' --permanent
Why it's wrong here
This allows SSH on port 22, not 2222.
- ✓
firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" port port="2222" protocol="tcp" accept' --permanent
Why this is correct
This restricts SSH to port 2222 from the specified subnet.
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 confuse the 'service name' with a custom port, selecting Option C which uses the SSH service (port 22) instead of the required port 2222, or they forget to restrict the source address as in Option B.
Detailed technical explanation
How to think about this question
Firewalld rich rules allow granular control using the 'rule' syntax, where 'family="ipv4"' restricts to IPv4 traffic, 'source address' limits the source network, and 'port port="2222" protocol="tcp"' specifies the exact port and protocol. The external zone typically has a default policy of 'drop' (or 'reject' in some configurations), so only rules that explicitly accept traffic will permit it; this rule overrides the default drop for the specified traffic.
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.
- →
Manage security — study guide chapter
Learn the concepts, then practise the questions
- →
Manage security practice questions
Targeted practice on this topic area only
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FAQ
Questions learners often ask
What does this EX200 question test?
Manage security — This question tests Manage security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" port port="2222" protocol="tcp" accept' --permanent — Option D is correct because it uses a rich rule to explicitly allow incoming TCP traffic on port 2222 from the 10.0.1.0/24 source network, which matches the requirement. The default target for the external zone is 'drop', so only explicitly permitted traffic is allowed; this rule ensures SSH on port 2222 is accepted while all other incoming traffic is dropped.
What should I do if I get this EX200 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.
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 →
Same concept, more angles
1 more ways this is tested on EX200
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. A host in the 192.168.1.0/24 network is unable to access a web service running on this server on port 8080. What is the most likely reason?
medium- A.The service http is not defined for port 8080.
- ✓ B.The rich rule only allows http (port 80), not the custom port 8080.
- C.The zone is internal and has a default target of drop.
- D.The interface eth1 is not added to the zone.
Why B: The rich rule in firewalld explicitly allows only HTTP traffic on port 80. Since the web service is running on port 8080, which is not covered by the rich rule, the firewall drops the connection. The default zone behavior does not override explicit rich rules, so the traffic is blocked.
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Last reviewed: Jun 24, 2026
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