- A
Allow traffic from the outside interface to the DMZ interface on port 80
This rule permits external traffic to reach the web server in the DMZ while keeping the internal network isolated.
- B
Allow traffic from the inside interface to the DMZ interface on port 80
Why wrong: This rule permits internal users, not external users, to access the web server.
- C
Allow traffic from the outside interface to the inside interface on port 80
Why wrong: This would expose the internal network to direct inbound traffic, defeating the purpose of a DMZ.
- D
Deny all traffic by default and create no specific rules
Why wrong: A default deny without an explicit allow rule would block all traffic, including legitimate web requests.
Question 286 of 520
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network 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 hosts a web server in a DMZ. The firewall has three interfaces: inside (corporate network), outside (Internet), and DMZ. Which firewall rule is necessary to allow external users to access the web server?
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
✓
Allow traffic from the outside interface to the DMZ interface on port 80
Option A is correct because external users on the Internet (outside interface) need to reach the web server located in the DMZ. The firewall must permit inbound traffic from the outside zone to the DMZ zone on TCP port 80 (HTTP) to allow web requests while keeping the corporate network (inside) isolated from direct external 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.
- ✓
Allow traffic from the outside interface to the DMZ interface on port 80
Why this is correct
This rule permits external traffic to reach the web server in the DMZ while keeping the internal network isolated.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Allow traffic from the inside interface to the DMZ interface on port 80
Why it's wrong here
This rule permits internal users, not external users, to access the web server.
When this WOULD be correct
This rule would be correct if the question asked for a rule allowing internal corporate users to access the web server hosted in the DMZ. For example: 'Which firewall rule allows employees on the corporate network to access the company's web server in the DMZ?'
- ✗
Allow traffic from the outside interface to the inside interface on port 80
Why it's wrong here
This would expose the internal network to direct inbound traffic, defeating the purpose of a DMZ.
When this WOULD be correct
This option would be correct if the question asked for a rule to allow internal users to access a web server located on the corporate network (inside interface) from the Internet, but that scenario is unrealistic. Alternatively, if the web server were on the inside interface and the goal was to allow external access, this rule would be needed, but that would be a poor security design.
- ✗
Deny all traffic by default and create no specific rules
Why it's wrong here
A default deny without an explicit allow rule would block all traffic, including legitimate web requests.
When this WOULD be correct
This option would be correct in a question asking for the default security posture of a firewall when no rules are configured, or in a scenario where the goal is to block all traffic and only allow specific traffic after creating explicit allow rules.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Allow traffic from the outside interface to the DMZ interface on port 80Correct answer▾
Why this is correct
This rule permits external traffic to reach the web server in the DMZ while keeping the internal network isolated.
✗Allow traffic from the inside interface to the DMZ interface on port 80Wrong answer — click to see why▾
Why this is wrong here
This rule allows traffic from the inside (corporate network) to the DMZ, which is not needed for external users to access the web server. External users come from the Internet (outside interface), not the inside network.
★ When this WOULD be the correct answer
This rule would be correct if the question asked for a rule allowing internal corporate users to access the web server hosted in the DMZ. For example: 'Which firewall rule allows employees on the corporate network to access the company's web server in the DMZ?'
Why candidates choose this
Candidates may confuse the direction of traffic needed for external access, mistakenly thinking that allowing traffic from the inside to the DMZ is sufficient, or they may not fully understand the role of each firewall interface.
✗Allow traffic from the outside interface to the inside interface on port 80Wrong answer — click to see why▾
Why this is wrong here
This rule would allow traffic from the Internet to the corporate network on port 80, which bypasses the DMZ and directly exposes internal resources, violating security best practices.
★ When this WOULD be the correct answer
This option would be correct if the question asked for a rule to allow internal users to access a web server located on the corporate network (inside interface) from the Internet, but that scenario is unrealistic. Alternatively, if the web server were on the inside interface and the goal was to allow external access, this rule would be needed, but that would be a poor security design.
Why candidates choose this
Candidates may confuse the direction of traffic or think that external users need to reach the inside network directly, misunderstanding the purpose of a DMZ as a buffer zone.
✗Deny all traffic by default and create no specific rulesWrong answer — click to see why▾
Why this is wrong here
Option D suggests denying all traffic by default and creating no specific rules, which would block all traffic including legitimate external access to the web server, making it impossible for external users to reach the server.
★ When this WOULD be the correct answer
This option would be correct in a question asking for the default security posture of a firewall when no rules are configured, or in a scenario where the goal is to block all traffic and only allow specific traffic after creating explicit allow rules.
Why candidates choose this
Candidates may think that 'deny all by default' is a secure baseline, but they forget that specific allow rules are needed to permit desired traffic; the option's wording implies no rules are created, which contradicts the requirement to allow access.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly choose Option B or C, confusing the direction of traffic or thinking that external users need access to the inside network, when the correct security design is to restrict external traffic only to the DMZ.
Detailed technical explanation
How to think about this question
In a three-legged firewall architecture, each interface belongs to a separate security zone, and traffic between zones is controlled by stateful inspection rules. The DMZ acts as a buffer zone where public-facing servers reside; allowing only necessary ports (e.g., TCP 80/443) from outside to DMZ ensures that even if the web server is compromised, the attacker cannot pivot directly to the inside network. Real-world deployments often add a rule to allow return traffic (established connections) and may use NAT to map a public IP to the DMZ server.
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
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Allow traffic from the outside interface to the DMZ interface on port 80 — Option A is correct because external users on the Internet (outside interface) need to reach the web server located in the DMZ. The firewall must permit inbound traffic from the outside zone to the DMZ zone on TCP port 80 (HTTP) to allow web requests while keeping the corporate network (inside) isolated from direct external access.
What should I do if I get this N10-009 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 →
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Last reviewed: Jun 11, 2026
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