The answer is a missing static NAT configuration for the server. This is the most likely cause because NAT hairpinning on a Cisco ASA requires a bidirectional mapping—typically created with the `static` keyword—so that internal traffic destined to the public IP 203.0.113.10 is correctly translated back to the server’s private IP 192.168.1.10. Without this explicit static NAT, the ASA sees the source IP as internal and the destination as the outside interface’s public IP, but lacks the necessary reverse translation, causing the packet to be dropped or misrouted. On the Cisco SCOR / CCNP Security Core 350-701 exam, this scenario tests your understanding of NAT hairpinning and the difference between one-way and two-way NAT translations. A common trap is assuming that a standard static NAT rule automatically handles internal-to-public traffic, but in reality, the `static` keyword must be applied to the NAT statement to enable the bidirectional flow. Memory tip: think “static for symmetric” — if traffic must return through the same path, the NAT rule must be explicitly bidirectional.
350-701 Network Security Practice Question
This 350-701 practice question tests your understanding of network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
configure terminal
access-list OUTSIDE extended permit tcp any host 203.0.113.10 eq www
access-list OUTSIDE extended permit udp any host 203.0.113.10 eq domain
nat (inside,outside) source dynamic any interface
Refer to the exhibit. An ASA is configured with the above access-list and NAT rule. A web server is reachable from the internet via the public IP 203.0.113.10. However, internal users from the inside network cannot access the web server using its public IP address. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The NAT rule is missing a static NAT for the server.
The correct answer is A because the NAT rule shown is a static NAT for the web server, but it is missing the 'static' keyword or the bidirectional mapping required for internal users to reach the server using its public IP. Without a proper static NAT (e.g., 'nat (inside,outside) static 192.168.1.10 service tcp www www'), the ASA does not translate the source IP of internal traffic destined to 203.0.113.10 back to the server's private IP, causing the traffic to be dropped or misrouted.
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.
✓
The NAT rule is missing a static NAT for the server.
Why this is correct
Without a static NAT, internal users cannot access the server via the public IP due to lack of hairpinning.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The access-list does not permit traffic from inside to outside for that destination.
Why it's wrong here
The ACL is applied on the outside interface, so it does not filter inside-to-outside traffic.
✗
The interface ACL is applied inbound on the inside interface.
Why it's wrong here
The ACL is applied to the outside interface, not inside.
✗
The default route is missing.
Why it's wrong here
A missing default route would affect traffic to the internet, but not specifically internal access to a public IP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a single static NAT rule automatically handles all traffic directions, but Cisco tests the nuance that internal-to-internal traffic via the public IP requires explicit NAT configuration (often called 'NAT reflection' or 'hairpinning'), which is not implied by a basic static NAT.
Detailed technical explanation
How to think about this question
Under the hood, ASA NAT operates with a concept of 'bidirectional' vs 'unidirectional' translation. A static NAT without the 'static' keyword (or without the 'nat (inside,outside)' syntax) creates only a one-way translation for traffic initiated from outside to inside. For internal users to access the server via its public IP, the ASA must perform a 'hairpin' or 'NAT reflection' where the source IP of the internal user is translated to the outside interface IP (or another routable IP) while the destination is translated to the private IP. This requires either a 'static' NAT with the 'dns' keyword or a separate 'nat (inside,inside)' rule to handle the traffic flow.
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.
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.
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: The NAT rule is missing a static NAT for the server. — The correct answer is A because the NAT rule shown is a static NAT for the web server, but it is missing the 'static' keyword or the bidirectional mapping required for internal users to reach the server using its public IP. Without a proper static NAT (e.g., 'nat (inside,outside) static 192.168.1.10 service tcp www www'), the ASA does not translate the source IP of internal traffic destined to 203.0.113.10 back to the server's private IP, causing the traffic to be dropped or misrouted.
What should I do if I get this 350-701 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. A host with IP address 10.0.0.5 sends traffic to destination 192.168.2.10. The traffic is not being translated. What is the most likely cause?
medium
A.The security-level of the inside interface is too high to allow NAT.
✓ B.The ACL INSIDE_NAT does not permit traffic to the destination network 192.168.2.0/24.
C.The interface outside does not have a valid IP address assigned.
Why B: The access-list INSIDE_NAT permits traffic to network 192.168.3.0/24, but the destination is 192.168.2.10, which is not matched. Therefore, NAT is not applied to that traffic. Option A is correct. Options B, C, and D are not relevant because dynamic NAT is allowed, outside interface has an IP, and security-level does not affect NAT.
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Question Discussion
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