- A
The interface is configured as both inside and outside, which is invalid.
NAT requires separate inside and outside interfaces.
- B
The interface is correctly configured for NAT.
Why wrong: Having both roles on one interface is not supported.
- C
The interface is down.
Why wrong: The output shows it is up.
- D
Overload is not active.
Why wrong: Overload is shown as active.
Question 572 of 2,152
NAT Interface Misconfiguration
This 300-410 practice question tests your understanding of nat and pat. 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 runs the following command to verify NAT on an interface:
R1# show ip nat interface GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is up NAT: inside, active NAT: outside, active NAT: overload, active
What is the issue with this configuration?
Quick Answer
The answer is that the interface is configured as both inside and outside, which is an invalid NAT configuration. This is incorrect because a single interface on a Cisco router cannot simultaneously serve as both the NAT inside and NAT outside; it must be designated as one or the other to properly define the direction of traffic translation. In the context of the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of NAT interface misconfiguration, a common trap where engineers mistakenly apply both ip nat inside and ip nat outside commands to the same interface, often during troubleshooting overload or dynamic NAT setups. The show ip nat interface output clearly reveals the conflict by listing both roles as active, which will cause unpredictable translation behavior or complete failure. A helpful memory tip is to think of NAT as a one-way door: an interface can only be the entrance (inside) or the exit (outside), never both at once.
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 interface is configured as both inside and outside, which is invalid.
The command output shows that GigabitEthernet0/1 is configured as both 'inside' and 'active' and 'outside' and 'active' simultaneously. In Cisco IOS NAT, an interface can be either a NAT inside interface or a NAT outside interface, but not both. This misconfiguration causes ambiguous NAT behavior because the router cannot determine whether traffic entering or leaving the interface should be translated from inside to outside or vice versa, leading to translation failures.
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 interface is configured as both inside and outside, which is invalid.
Why this is correct
NAT requires separate inside and outside interfaces.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The interface is correctly configured for NAT.
Why it's wrong here
Having both roles on one interface is not supported.
- ✗
The interface is down.
Why it's wrong here
The output shows it is up.
- ✗
Overload is not active.
Why it's wrong here
Overload is shown as active.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that an interface can be both inside and outside for NAT, leading candidates to overlook the explicit 'inside' and 'outside' flags in the 'show ip nat interface' output and incorrectly assume the configuration is valid.
Trap categories for this question
Command / output trap
The output shows it is up.
Detailed technical explanation
How to think about this question
Cisco NAT uses the 'ip nat inside' and 'ip nat outside' commands to designate interface roles, and these roles are mutually exclusive per interface because NAT translation logic relies on a clear inside-to-outside direction. When both are applied, the router's CEF and NAT engine may produce unpredictable results, such as failing to translate packets or creating duplicate NAT entries. In real-world scenarios, this often occurs when an engineer mistakenly applies both commands to a single interface on a router running IOS 15.x, leading to intermittent connectivity issues that are hard to debug without checking the interface NAT status.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 300-410 question test?
NAT and PAT — This question tests NAT and PAT — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The interface is configured as both inside and outside, which is invalid. — The command output shows that GigabitEthernet0/1 is configured as both 'inside' and 'active' and 'outside' and 'active' simultaneously. In Cisco IOS NAT, an interface can be either a NAT inside interface or a NAT outside interface, but not both. This misconfiguration causes ambiguous NAT behavior because the router cannot determine whether traffic entering or leaving the interface should be translated from inside to outside or vice versa, leading to translation failures.
What should I do if I get this 300-410 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: Jul 4, 2026
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