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?
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.
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 — 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.
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Question Discussion
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