- A
The static NAT should use a specific global IP address instead of the interface; configure ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80.
Using the interface IP for static NAT is not supported; a specific global IP must be defined.
- B
The access-list 100 is blocking inbound traffic.
Why wrong: ACL 100 is for dynamic NAT, not static NAT, and inbound traffic is not matched by it.
- C
The Loopback0 interface is not in the routing table.
Why wrong: Loopback0 is a virtual interface and is always up, but it is not the correct interface for NAT.
- D
The static NAT entry is missing the 'add-route' option.
Why wrong: The 'add-route' option is for route maps, not required for static NAT.
Question 533 of 2,152
300-410 NAT and PAT Practice Question
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.
Router R1 is configured with ip nat inside source list 100 interface Loopback0 overload. Internal hosts at 192.168.1.0/24 can access the internet, but external hosts cannot initiate connections to an internal server at 10.1.1.10 that is also behind NAT. The server is supposed to be reachable via static NAT. Configuration: ip nat inside source static tcp 10.1.1.10 80 interface Loopback0 80. Router R1 shows: show ip nat translations: Pro Inside global Inside local Outside local Outside global tcp 10.1.1.10:80 10.1.1.10:80 --- ---. External users get connection timeouts. What is the root cause?
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 static NAT should use a specific global IP address instead of the interface; configure ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80.
The static NAT configuration uses 'interface Loopback0' as the global address, which means it relies on the interface's dynamically assigned IP address. However, the overload rule (PAT) is also using the same interface, and the static NAT entry shown in 'show ip nat translations' displays the inside local address as the inside global address (10.1.1.10:80), indicating that the static translation is not being applied correctly. The root cause is that static NAT requires a specific global IP address (e.g., 203.0.113.10) to map the internal server, not the interface keyword, because the interface keyword is used for PAT and does not create a fixed one-to-one mapping for inbound connections.
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 static NAT should use a specific global IP address instead of the interface; configure ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80.
Why this is correct
Using the interface IP for static NAT is not supported; a specific global IP must be defined.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The access-list 100 is blocking inbound traffic.
- ✗
The Loopback0 interface is not in the routing table.
Why it's wrong here
Loopback0 is a virtual interface and is always up, but it is not the correct interface for NAT.
- ✗
The static NAT entry is missing the 'add-route' option.
Why it's wrong here
The 'add-route' option is for route maps, not required for static NAT.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between using 'interface' for dynamic PAT and a specific IP for static NAT, trapping candidates who think 'interface' can serve both purposes without understanding that static NAT requires a fixed global address for inbound reachability.
Detailed technical explanation
How to think about this question
When using 'interface' in a static NAT command, the router attempts to use the interface's primary IP address as the global address, but this conflicts with PAT because PAT dynamically translates multiple inside addresses to the same interface IP, and static NAT expects a dedicated global IP. Under the hood, the NAT table shows the inside local address as the inside global because the translation is not binding to a routable global IP, causing return traffic to be dropped. In real-world scenarios, this is common when engineers mistakenly assume 'interface' works for both dynamic and static translations, leading to asymmetric routing and connection timeouts for inbound traffic.
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
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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 static NAT should use a specific global IP address instead of the interface; configure ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80. — The static NAT configuration uses 'interface Loopback0' as the global address, which means it relies on the interface's dynamically assigned IP address. However, the overload rule (PAT) is also using the same interface, and the static NAT entry shown in 'show ip nat translations' displays the inside local address as the inside global address (10.1.1.10:80), indicating that the static translation is not being applied correctly. The root cause is that static NAT requires a specific global IP address (e.g., 203.0.113.10) to map the internal server, not the interface keyword, because the interface keyword is used for PAT and does not create a fixed one-to-one mapping for inbound connections.
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.
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Last reviewed: Jul 4, 2026
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