- A
Enable NAT hairpinning by configuring ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80 and ensuring the router has a route to the public IP.
Hairpinning allows the router to forward traffic from inside to inside via the public IP.
- B
Configure the host to use the private IP of the server instead of the public IP.
Why wrong: This is a workaround, not a fix for the NAT issue.
- C
Add a static route on the router for 203.0.113.10 pointing to the server.
Why wrong: This does not address the NAT hairpinning problem.
- D
Use ip nat outside source list 100 interface GigabitEthernet0/1 overload.
Why wrong: This would translate outside addresses, not solve hairpinning.
Question 504 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 GigabitEthernet0/1 overload. Internal host 192.168.1.10 can access the internet, but when it tries to connect to an internal server at 10.1.1.10 via its public IP 203.0.113.10, the connection fails. Router R1 shows: show ip nat translations: Pro Inside global Inside local Outside local Outside global --- 203.0.113.10 10.1.1.10 --- ---. The host's traffic is being NATed to 203.0.113.1, but the server's response is sent to 203.0.113.1. 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
✓
Enable NAT hairpinning by configuring ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80 and ensuring the router has a route to the public IP.
The root cause is that NAT hairpinning (also known as NAT reflection or NAT loopback) is not enabled. When an internal host (192.168.1.10) tries to reach an internal server (10.1.1.10) using the server's public IP (203.0.113.10), the router performs NAT for the host's traffic, translating its source to 203.0.113.1. The server's response is sent to 203.0.113.1 (the router's outside interface), but without hairpinning, the router does not know to forward this response back to the internal host because it expects the traffic to come from the outside. Option A corrects this by adding a static NAT for the server (mapping 10.1.1.10:80 to 203.0.113.10:80) and ensuring the router has a route to the public IP, which enables the router to perform the necessary NAT translation and forward the response back to the internal host.
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.
- ✓
Enable NAT hairpinning by configuring ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80 and ensuring the router has a route to the public IP.
Why this is correct
Hairpinning allows the router to forward traffic from inside to inside via the public IP.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure the host to use the private IP of the server instead of the public IP.
Why it's wrong here
This is a workaround, not a fix for the NAT issue.
- ✗
Add a static route on the router for 203.0.113.10 pointing to the server.
Why it's wrong here
This does not address the NAT hairpinning problem.
- ✗
Use ip nat outside source list 100 interface GigabitEthernet0/1 overload.
Why it's wrong here
This would translate outside addresses, not solve hairpinning.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that NAT hairpinning is automatically handled by dynamic PAT, when in fact it requires explicit static NAT configuration and a route to the public IP to force the router to perform the necessary translations.
Detailed technical explanation
How to think about this question
NAT hairpinning requires the router to process packets that arrive on an inside interface and are destined for a public IP that is also mapped to an inside host. The router must perform a destination NAT (DNAT) to translate the public IP back to the private IP, and then a source NAT (SNAT) to ensure the response is routed correctly. This behavior is not automatic with dynamic PAT; it requires explicit static NAT entries or the 'ip nat enable' command on the interface, along with a route to the public IP (often a loopback or null route) to force the router to process the traffic. In real-world scenarios, this is critical for services like internal email servers or web servers that must be accessible via their public IP from within the same network.
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.
- →
NAT and PAT — study guide chapter
Learn the concepts, then practise the questions
- →
NAT and PAT practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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: Enable NAT hairpinning by configuring ip nat inside source static tcp 10.1.1.10 80 203.0.113.10 80 and ensuring the router has a route to the public IP. — The root cause is that NAT hairpinning (also known as NAT reflection or NAT loopback) is not enabled. When an internal host (192.168.1.10) tries to reach an internal server (10.1.1.10) using the server's public IP (203.0.113.10), the router performs NAT for the host's traffic, translating its source to 203.0.113.1. The server's response is sent to 203.0.113.1 (the router's outside interface), but without hairpinning, the router does not know to forward this response back to the internal host because it expects the traffic to come from the outside. Option A corrects this by adding a static NAT for the server (mapping 10.1.1.10:80 to 203.0.113.10:80) and ensuring the router has a route to the public IP, which enables the router to perform the necessary NAT translation and forward the response back to the internal host.
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 →
Keep practising
More 300-410 practice questions
- Drag and drop the steps to negotiate an IKEv2 IPsec site-to-site tunnel into the correct order, from first to last.
- Drag and drop the steps to troubleshoot an IPsec site-to-site VPN adjacency failure into the correct order, from first t…
- Drag and drop the steps to verify and validate the operational state of an IPsec site-to-site VPN into the correct order…
- Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.25…
- A router is configured with 'logging host 10.1.1.100' and 'logging trap informational'. The engineer notices that syslog…
- Drag and drop the steps to configure a GRE tunnel for IPv6 over IPv4 into the correct order, from first to last.
Last reviewed: Jul 4, 2026
This 300-410 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 300-410 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.