- A
Perfect Forward Secrecy (PFS)
Why wrong: A security feature for keying, not related to NAT.
- B
NAT Traversal (NAT-T)
Required to encapsulate IPsec in UDP to pass through NAT.
- C
Dead Peer Detection (DPD)
Why wrong: Used to detect if the peer is alive, not for NAT.
- D
IKEv2
Why wrong: A version of IKE, but not specifically for NAT traversal.
Question 1,580 of 1,705
VPN NAT Traversal (NAT-T) for Site-to-Site VPN
This ANS-C01 practice question tests your understanding of network implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 company is setting up a Site-to-Site VPN connection to AWS. The customer gateway device is behind a NAT device that performs address translation. Which tunnel option must be enabled to ensure the VPN tunnel establishes correctly?
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
✓
NAT Traversal (NAT-T)
When a customer gateway device is behind a NAT device, the NAT device modifies the IP addresses and potentially the UDP ports in the IPsec packet headers. Standard IPsec (ESP) does not work through NAT because ESP is a Layer 4 protocol with no port numbers. NAT Traversal (NAT-T) solves this by encapsulating IPsec packets inside UDP (typically port 4500), allowing the NAT device to perform address translation without breaking the VPN tunnel.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that IKEv2 alone solves NAT traversal, but in reality, NAT-T is a separate mechanism that must be enabled or negotiated regardless of the IKE version, and simply using IKEv2 does not automatically enable UDP encapsulation for ESP traffic.
Detailed technical explanation
How to think about this question
NAT-T works by detecting whether a NAT device is present between the VPN endpoints during IKE phase 1 (via the exchange of vendor ID payloads and checking if the source IP differs from the IKE source IP). Once detected, the IPsec stack encapsulates ESP packets in UDP datagrams (port 4500) to preserve the original IP header and port information, allowing the NAT device to translate addresses correctly. In real-world scenarios, if NAT-T is not enabled, the VPN tunnel may appear to establish (IKE phases succeed) but data traffic (ESP) will be silently dropped by the NAT device, leading to a 'one-way' or completely broken tunnel.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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.
- →
Network Implementation — study guide chapter
Learn the concepts, then practise the questions
- →
Network Implementation practice questions
Targeted practice on this topic area only
- →
All ANS-C01 questions
1,705 questions across all exam domains
- →
AWS Certified Advanced Networking Specialty ANS-C01 study guide
Full concept coverage aligned to exam objectives
- →
ANS-C01 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related ANS-C01 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network Management and Operations practice questions
Practise ANS-C01 questions linked to Network Management and Operations.
Network Security, Compliance and Governance practice questions
Practise ANS-C01 questions linked to Network Security, Compliance and Governance.
Network Design practice questions
Practise ANS-C01 questions linked to Network Design.
Network Implementation practice questions
Practise ANS-C01 questions linked to Network Implementation.
ANS-C01 fundamentals practice questions
Practise ANS-C01 questions linked to ANS-C01 fundamentals.
ANS-C01 scenario practice questions
Practise ANS-C01 questions linked to ANS-C01 scenario.
ANS-C01 troubleshooting practice questions
Practise ANS-C01 questions linked to ANS-C01 troubleshooting.
Practice this exam
Start a free ANS-C01 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 ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NAT Traversal (NAT-T) — When a customer gateway device is behind a NAT device, the NAT device modifies the IP addresses and potentially the UDP ports in the IPsec packet headers. Standard IPsec (ESP) does not work through NAT because ESP is a Layer 4 protocol with no port numbers. NAT Traversal (NAT-T) solves this by encapsulating IPsec packets inside UDP (typically port 4500), allowing the NAT device to perform address translation without breaking the VPN tunnel.
What should I do if I get this ANS-C01 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 ANS-C01 practice questions
- A financial services company has a VPC with a public subnet and a private subnet. EC2 instances in the private subnet ne…
- A company is designing a network security architecture for a multi-account environment using AWS Transit Gateway. The se…
- A company is using AWS Direct Connect to connect its on-premises network to AWS. The company wants to encrypt all traffi…
- A company uses AWS Transit Gateway to connect multiple VPCs and on-premises networks via AWS Site-to-Site VPN. The secur…
- A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application must be acc…
- A global e-commerce company uses a hub-and-spoke network topology with a transit VPC in us-east-1. Each spoke VPC has an…
Last reviewed: Jul 4, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 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.