- A
The ACL is too permissive; it should only permit specific hosts.
Why wrong: The ACL is correctly permitting the inside network.
- B
The interface GigabitEthernet0/1 is missing the 'ip nat outside' command.
Without 'ip nat outside', the router does not know which interface is the outside for NAT.
- C
The 'overload' keyword is unnecessary for this configuration.
Why wrong: Overload is needed for PAT, which is likely intended.
- D
The inside interface should be GigabitEthernet0/1.
Why wrong: Inside/outside designations are correct; only the outside interface is missing the command.
Question 76 of 2,152
NAT Configuration Error — Missing ip nat outside Command | Cisco CCNP ENARSI 300-410 Explained
This 300-410 practice question tests your understanding of nat and pat. 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.
What is the problem with this NAT configuration?
interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip nat inside
!
interface GigabitEthernet0/1 ip address 203.0.113.1 255.255.255.0
!
ip nat inside source list 1 interface GigabitEthernet0/1 overload access-list 1 permit 192.168.1.0 0.0.0.255
Quick Answer
The answer is that the interface GigabitEthernet0/1 is missing the ip nat outside command. This is the root cause of the NAT configuration error because Cisco IOS requires both an ip nat inside and an ip nat outside designation on the respective interfaces for translation to occur; without the outside command on the public-facing interface, the router has no egress point to apply the source NAT rule. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of the fundamental two-interface NAT model, often appearing as a subtle misconfiguration trap where candidates focus on the access list or the overload keyword while overlooking the missing interface directive. A common memory tip is to remember that NAT is like a door—you must label both the inside and the outside for traffic to pass through, so always verify both ip nat inside and ip nat outside are present in your configuration.
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 GigabitEthernet0/1 is missing the 'ip nat outside' command.
The configuration is missing the 'ip nat outside' command on interface GigabitEthernet0/1. For NAT to function, Cisco IOS requires that the inside interface be marked with 'ip nat inside' and the outside interface with 'ip nat outside'. Without this, the router does not know which interface is the external (outside) interface, and the NAT translation will not be applied to outgoing packets.
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 ACL is too permissive; it should only permit specific hosts.
Why it's wrong here
The ACL is correctly permitting the inside network.
- ✓
The interface GigabitEthernet0/1 is missing the 'ip nat outside' command.
Why this is correct
Without 'ip nat outside', the router does not know which interface is the outside for NAT.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The 'overload' keyword is unnecessary for this configuration.
Why it's wrong here
Overload is needed for PAT, which is likely intended.
- ✗
The inside interface should be GigabitEthernet0/1.
Why it's wrong here
Inside/outside designations are correct; only the outside interface is missing the command.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume that simply configuring the NAT statement and ACL is enough, overlooking the mandatory interface-level 'ip nat outside' command, which Cisco explicitly tests in the 300-410 exam to ensure understanding of NAT operation fundamentals.
Trap categories for this question
Command / output trap
Inside/outside designations are correct; only the outside interface is missing the command.
Detailed technical explanation
How to think about this question
Under the hood, Cisco IOS NAT uses the 'ip nat inside' and 'ip nat outside' interface commands to build a NAT translation table and determine the direction of translation. When a packet enters an inside interface and exits an outside interface, the router checks the ACL and creates a dynamic translation entry with the source IP and port (if overload is used). A common real-world scenario is a branch office router where the WAN interface is a DHCP-assigned public IP; forgetting 'ip nat outside' is a frequent misconfiguration that causes all traffic to fail NAT translation, even though the ACL and inside interface are correct.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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 GigabitEthernet0/1 is missing the 'ip nat outside' command. — The configuration is missing the 'ip nat outside' command on interface GigabitEthernet0/1. For NAT to function, Cisco IOS requires that the inside interface be marked with 'ip nat inside' and the outside interface with 'ip nat outside'. Without this, the router does not know which interface is the external (outside) interface, and the NAT translation will not be applied to outgoing packets.
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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