- A
Allow traffic from Outside to DMZ on port 443
This rule permits HTTPS traffic from the Internet (Outside) to the web server in the DMZ, which is the requirement.
- B
Allow traffic from DMZ to Outside on port 443
Why wrong: This rule permits outbound traffic from the DMZ to the Internet, which would allow the web server to initiate outbound connections, but does not allow inbound HTTPS requests.
- C
Allow traffic from Inside to DMZ on port 443
Why wrong: This rule permits internal corporate users to access the web server, but not external users from the Internet.
- D
Allow traffic from Outside to Inside on port 443
Why wrong: This would allow inbound traffic directly into the corporate network, bypassing the DMZ, which is not the intention and violates security best practices.
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 wants to allow inbound HTTPS traffic to a web server located in the DMZ from the Internet. The firewall has three interfaces: Inside (corporate network), Outside (Internet), and DMZ (web server). Which of the following firewall rules is required?
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 Outside to DMZ on port 443
The correct rule is to allow traffic from the Outside (Internet) interface to the DMZ interface on TCP port 443 (HTTPS). This permits inbound web requests to reach the web server while keeping the corporate Inside network isolated. The firewall must explicitly permit this traffic because the default implicit deny rule would otherwise block all inbound connections from the Outside zone.
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 Outside to DMZ on port 443
Why this is correct
This rule permits HTTPS traffic from the Internet (Outside) to the web server in the DMZ, which is the requirement.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Allow traffic from DMZ to Outside on port 443
Why it's wrong here
This rule permits outbound traffic from the DMZ to the Internet, which would allow the web server to initiate outbound connections, but does not allow inbound HTTPS requests.
When this WOULD be correct
This option would be correct if the question required allowing the web server in the DMZ to initiate outbound HTTPS connections to the Internet, for example, to download updates or access external APIs.
- ✗
Allow traffic from Inside to DMZ on port 443
Why it's wrong here
This rule permits internal corporate users to access the web server, but not external users from the Internet.
When this WOULD be correct
This option would be correct if the question asked for a rule to allow internal corporate users (Inside) to access a web server in the DMZ for management or internal applications.
- ✗
Allow traffic from Outside to Inside on port 443
Why it's wrong here
This would allow inbound traffic directly into the corporate network, bypassing the DMZ, which is not the intention and violates security best practices.
When this WOULD be correct
This rule would be correct if the web server were located on the Inside interface (corporate network) and the company wanted to allow inbound HTTPS from the internet directly to that internal server, though this is generally discouraged due to security risks.
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 Outside to DMZ on port 443Correct answer▾
Why this is correct
This rule permits HTTPS traffic from the Internet (Outside) to the web server in the DMZ, which is the requirement.
✗Allow traffic from DMZ to Outside on port 443Wrong answer — click to see why▾
Why this is wrong here
The question asks for a rule to allow inbound HTTPS traffic from the Internet to the web server in the DMZ. Option B allows traffic from DMZ to Outside, which is outbound, not inbound, and does not permit the initial connection from the Internet.
★ When this WOULD be the correct answer
This option would be correct if the question required allowing the web server in the DMZ to initiate outbound HTTPS connections to the Internet, for example, to download updates or access external APIs.
Why candidates choose this
Candidates may confuse the direction of traffic or think that allowing return traffic from the DMZ is necessary for the inbound connection, not realizing that stateful firewalls automatically permit return traffic for established connections.
✗Allow traffic from Inside to DMZ on port 443Wrong answer — click to see why▾
Why this is wrong here
The question specifies inbound HTTPS traffic from the Internet to a web server in the DMZ, so the rule must allow traffic from Outside to DMZ, not from Inside to DMZ.
★ When this WOULD be the correct answer
This option would be correct if the question asked for a rule to allow internal corporate users (Inside) to access a web server in the DMZ for management or internal applications.
Why candidates choose this
Candidates may confuse the direction of traffic or think that internal users need access to the DMZ web server, overlooking that the question explicitly states traffic originates from the Internet.
✗Allow traffic from Outside to Inside on port 443Wrong answer — click to see why▾
Why this is wrong here
The question specifies the web server is in the DMZ, not the Inside network. Allowing traffic from Outside to Inside on port 443 would bypass the DMZ and expose the internal corporate network to inbound internet traffic, violating security best practices.
★ When this WOULD be the correct answer
This rule would be correct if the web server were located on the Inside interface (corporate network) and the company wanted to allow inbound HTTPS from the internet directly to that internal server, though this is generally discouraged due to security risks.
Why candidates choose this
Candidates may confuse the DMZ with the Inside network or assume that HTTPS traffic should be allowed to any internal server, overlooking the specific placement of the web server in the DMZ as stated in the question.
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 often confuse the direction of the traffic flow, mistakenly thinking the rule should allow traffic from the DMZ to the Outside (Option B) because they focus on the server sending responses, rather than the client initiating the connection.
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 must be explicitly permitted by stateful inspection rules. The firewall tracks connection state; for inbound HTTPS, the rule must match the initial SYN packet from Outside to DMZ, and the return traffic is automatically allowed by the state table. Real-world deployments often combine this rule with NAT (port forwarding) to map a public IP to the private DMZ server address.
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.
Visual reference
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 Outside to DMZ on port 443 — The correct rule is to allow traffic from the Outside (Internet) interface to the DMZ interface on TCP port 443 (HTTPS). This permits inbound web requests to reach the web server while keeping the corporate Inside network isolated. The firewall must explicitly permit this traffic because the default implicit deny rule would otherwise block all inbound connections from the Outside zone.
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.
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Last reviewed: Jun 11, 2026
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