- A
The access list used for NAT does not permit the web server's IP address.
Why wrong: Incorrect because the access list is used to identify which inside local addresses are eligible for translation; it does not affect static mappings.
- B
The engineer forgot to add the ip nat inside source static command for the web server.
Correct because a static NAT entry is required to map the public IP to the internal web server's private IP, allowing inbound connections.
- C
The ip nat inside and ip nat outside commands are applied on the wrong interfaces.
Why wrong: Incorrect because the scenario does not indicate an interface misapplication; the issue is the lack of a static mapping.
- D
The global configuration mode is missing the ip nat pool command.
Why wrong: Incorrect because a pool is not required for static NAT; it is used for dynamic NAT with multiple addresses.
CCNP NAT and DHCP Practice Question
This 350-401 practice question tests your understanding of nat and dhcp. 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.
A network engineer is configuring a Cisco router to provide internet access to a small office using a single public IP address assigned by the ISP. The engineer wants to allow internal hosts to initiate connections to the internet, but also needs to make a web server on the internal network reachable from the internet. The engineer configures a standard access list for NAT and an ip nat inside source list command. However, external users cannot reach the internal web server. 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 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
The engineer forgot to add the ip nat inside source static command for the web server.
The scenario requires both dynamic NAT (for outbound traffic) and static NAT (for inbound access to the web server). Using only a dynamic NAT configuration with an access list will not provide a permanent mapping for the web server.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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 access list used for NAT does not permit the web server's IP address.
Why it's wrong here
Incorrect because the access list is used to identify which inside local addresses are eligible for translation; it does not affect static mappings.
- ✓
The engineer forgot to add the ip nat inside source static command for the web server.
Why this is correct
Correct because a static NAT entry is required to map the public IP to the internal web server's private IP, allowing inbound connections.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
- ✗
The ip nat inside and ip nat outside commands are applied on the wrong interfaces.
Why it's wrong here
Incorrect because the scenario does not indicate an interface misapplication; the issue is the lack of a static mapping.
- ✗
The global configuration mode is missing the ip nat pool command.
Why it's wrong here
Incorrect because a pool is not required for static NAT; it is used for dynamic NAT with multiple addresses.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Trap categories for this question
Scenario analysis trap
Incorrect because the scenario does not indicate an interface misapplication; the issue is the lack of a static mapping.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
- Authentication checks who the user is.
- Authorization controls what the user is allowed to do after login.
- Privilege levels affect access to EXEC and configuration commands.
- AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
- Do not assume successful login means full administrative access.
- Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
- Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-401 questions on access control and AAA configuration.
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NAT and DHCP — study guide chapter
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FAQ
Questions learners often ask
What does this 350-401 question test?
NAT and DHCP — This question tests NAT and DHCP — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The engineer forgot to add the ip nat inside source static command for the web server. — The scenario requires both dynamic NAT (for outbound traffic) and static NAT (for inbound access to the web server). Using only a dynamic NAT configuration with an access list will not provide a permanent mapping for the web server.
What should I do if I get this 350-401 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-401 questions on access control and AAA configuration.
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?
Authentication checks who the user is.
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Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco 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 350-401 exam.
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