The answer is Destination NAT (DNAT). This is the correct choice because DNAT specifically translates the destination IP address of inbound packets from a public IP to a private server IP, which is exactly what is needed to allow external HTTPS traffic to reach an internal web server. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how firewalls handle inbound traffic from the internet to private addresses, often contrasting DNAT with SNAT (which translates source addresses for outbound traffic). A common trap is confusing DNAT with port forwarding or static NAT, but remember: DNAT rewrites the destination, not the source. For a quick memory tip, think “DNAT = Destination = Inbound,” and recall that in Cisco IOS, the ‘ip nat inside source static’ command handles this by treating the “inside” as the translated destination for traffic coming in.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 security analyst is configuring a firewall to allow HTTPS traffic from the internet to an internal web server with a private IP address. The firewall must translate the destination IP address of incoming packets to the private server IP. Which type of NAT should be configured?
Why wrong: SNAT translates the source IP address of outgoing packets, not the destination of incoming packets.
B
Destination NAT (DNAT)
DNAT modifies the destination IP address of incoming packets, allowing them to be forwarded to an internal server.
C
Static NAT
Why wrong: Static NAT provides a one-to-one mapping between a public and private IP address, but it is not specifically for translating the destination of inbound traffic; it translates both source and destination.
D
Port Address Translation (PAT)
Why wrong: PAT is a form of SNAT that uses port numbers to map multiple private IPs to a single public IP; it is used for outbound traffic, not inbound destination translation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Destination NAT (DNAT)
Destination NAT (DNAT) is used to translate the destination IP address of incoming packets from a public IP to a private IP, allowing external HTTPS traffic to reach an internal web server. This is exactly what the scenario requires: the firewall must rewrite the destination address of packets arriving from the internet to the private server IP. DNAT is commonly implemented using the 'ip nat inside source static' command in Cisco IOS, where the 'inside' keyword refers to the translation of destination addresses for inbound traffic.
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.
✗
Source NAT (SNAT)
Why it's wrong here
SNAT translates the source IP address of outgoing packets, not the destination of incoming packets.
✓
Destination NAT (DNAT)
Why this is correct
DNAT modifies the destination IP address of incoming packets, allowing them to be forwarded to an internal server.
Related concept
Read the scenario before looking for a memorised answer.
✗
Static NAT
Why it's wrong here
Static NAT provides a one-to-one mapping between a public and private IP address, but it is not specifically for translating the destination of inbound traffic; it translates both source and destination.
✗
Port Address Translation (PAT)
Why it's wrong here
PAT is a form of SNAT that uses port numbers to map multiple private IPs to a single public IP; it is used for outbound traffic, not inbound destination translation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between SNAT and DNAT by describing a scenario where traffic comes from the internet to an internal server, and candidates mistakenly choose SNAT because they think 'source' refers to the packet's origin (the internet), when in fact SNAT always translates the source address of outbound traffic, not the destination of inbound traffic.
Detailed technical explanation
How to think about this question
Under the hood, DNAT works by modifying the destination IP address in the IP header of incoming packets as they traverse the firewall, typically using a NAT table entry that maps a public IP (and optionally a port) to a private IP. In Cisco IOS, this is configured with 'ip nat inside source static tcp <public-ip> <port> <private-ip> <port> extendable', which creates a static DNAT rule. A subtle behavior is that DNAT often requires a corresponding route on the firewall to ensure return traffic is un-translated correctly, and it is commonly used with 'ip nat outside' and 'ip nat inside' interface designations to control which direction the translation applies.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
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: Destination NAT (DNAT) — Destination NAT (DNAT) is used to translate the destination IP address of incoming packets from a public IP to a private IP, allowing external HTTPS traffic to reach an internal web server. This is exactly what the scenario requires: the firewall must rewrite the destination address of packets arriving from the internet to the private server IP. DNAT is commonly implemented using the 'ip nat inside source static' command in Cisco IOS, where the 'inside' keyword refers to the translation of destination addresses for inbound traffic.
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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