The correct answer is the rule set that uses `iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT` followed by `iptables -A INPUT -i eth1 -p tcp --dport 22 -j DROP`. This works because iptables processes rules sequentially, so the explicit ACCEPT for SSH on the public interface (eth0) is matched first for that traffic, while the subsequent DROP rule catches any SSH attempts arriving on the private interface (eth1), effectively allowing SSH only on the public interface. On the LPIC-2 exam, this scenario tests your understanding of interface-based filtering and rule ordering—a common trap is forgetting that a default DROP policy would block the ACCEPT rule if placed before it, or mistakenly using the `-o` (output) flag instead of `-i` (input). The key concept is that iptables can restrict services to specific network paths, which is critical for securing multi-homed servers. Memory tip: think "eth0 first, then drop the rest"—always place your ACCEPT rules before any DROP rules for the same port to avoid accidental blocking.
LPIC-2 Advanced Networking Configuration Practice Question
This LPIC-2 practice question tests your understanding of advanced networking configuration. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 has a server with two network interfaces: eth0 (public IP) and eth1 (private IP). The administrator wants to allow SSH from the public network only. Which iptables rule set achieves this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT; iptables -A INPUT -i eth1 -p tcp --dport 22 -j DROP
Option A is correct because it explicitly allows SSH (TCP port 22) traffic arriving on the public interface (eth0) and then drops SSH traffic on the private interface (eth1). This ensures SSH is only accessible from the public network while blocking it on the private network. The order of rules matters: the ACCEPT rule for eth0 must come before any default DROP policy or later rules that might affect it.
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.
✓
iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT; iptables -A INPUT -i eth1 -p tcp --dport 22 -j DROP
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often forget that iptables rules are evaluated in order, so placing a broad DROP rule before a specific ACCEPT rule will cause the DROP to match first, inadvertently blocking the intended traffic.
Detailed technical explanation
How to think about this question
iptables processes rules in order; the first matching rule determines the packet's fate. In this scenario, the default INPUT policy is typically ACCEPT, so without explicit DROP rules, SSH would be allowed on both interfaces. The -i flag matches the incoming interface, which is critical for multi-homed hosts. In real-world deployments, administrators often combine this with stateful rules (e.g., -m state --state NEW) to only allow new SSH connections from the public interface while permitting established ones from any interface.
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 LPIC-2 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.
Advanced Networking Configuration — This question tests Advanced Networking Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT; iptables -A INPUT -i eth1 -p tcp --dport 22 -j DROP — Option A is correct because it explicitly allows SSH (TCP port 22) traffic arriving on the public interface (eth0) and then drops SSH traffic on the private interface (eth1). This ensures SSH is only accessible from the public network while blocking it on the private network. The order of rules matters: the ACCEPT rule for eth0 must come before any default DROP policy or later rules that might affect it.
What should I do if I get this LPIC-2 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 →
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.
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 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.