- A
Transport mode
Why wrong: Transport mode encrypts only the payload, not the original IP header, so it is not suitable for site-to-site VPNs where the entire packet must be hidden.
- B
Tunnel mode
Tunnel mode encapsulates the entire original IP packet with a new header, encrypting everything. This is the standard mode for site-to-site IPsec VPNs.
- C
AH only
Why wrong: AH provides authentication but no encryption, so it does not meet the encryption requirement.
- D
ESP only
Why wrong: ESP provides encryption but can be used in either transport or tunnel mode. The question asks which mode encrypts the entire packet including the header; that is tunnel mode, not just using ESP.
Question 226 of 520
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. 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 security engineer is configuring a site-to-site VPN between two branch offices. The requirement is to encrypt all traffic between the two networks using IPsec. Which IPsec mode should be used to encrypt the entire IP packet including the original header?
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
✓
Tunnel mode
Tunnel mode is the correct choice because it encrypts the entire original IP packet, including the original header, and then encapsulates it within a new IP header. This is required for site-to-site VPNs where the original source and destination IP addresses must be hidden or protected, and the new header is used for routing between the two VPN gateways.
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.
- ✗
Transport mode
Why it's wrong here
Transport mode encrypts only the payload, not the original IP header, so it is not suitable for site-to-site VPNs where the entire packet must be hidden.
When this WOULD be correct
Transport mode would be correct when the VPN is used for end-to-end communication between two hosts (e.g., a client and server) and the requirement is to encrypt only the payload while preserving the original IP header for routing.
- ✓
Tunnel mode
Why this is correct
Tunnel mode encapsulates the entire original IP packet with a new header, encrypting everything. This is the standard mode for site-to-site IPsec VPNs.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AH only
Why it's wrong here
AH provides authentication but no encryption, so it does not meet the encryption requirement.
When this WOULD be correct
When the requirement is only to authenticate and ensure integrity of IP packets without encryption, such as in a scenario where data confidentiality is not needed but protection against tampering is required.
- ✗
ESP only
Why it's wrong here
ESP provides encryption but can be used in either transport or tunnel mode. The question asks which mode encrypts the entire packet including the header; that is tunnel mode, not just using ESP.
When this WOULD be correct
A question asking: 'Which IPsec protocol provides encryption but not authentication of the IP header?' would make ESP only correct, as AH provides authentication but not encryption.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Tunnel modeCorrect answer▾
Why this is correct
Tunnel mode encapsulates the entire original IP packet with a new header, encrypting everything. This is the standard mode for site-to-site IPsec VPNs.
✗Transport modeWrong answer — click to see why▾
Why this is wrong here
Transport mode only encrypts the payload of the IP packet, leaving the original IP header intact, so it does not encrypt the entire packet including the header as required.
★ When this WOULD be the correct answer
Transport mode would be correct when the VPN is used for end-to-end communication between two hosts (e.g., a client and server) and the requirement is to encrypt only the payload while preserving the original IP header for routing.
Why candidates choose this
Candidates may confuse transport mode with tunnel mode, thinking both encrypt the entire packet, or they may not fully understand that transport mode excludes the header from encryption.
✗AH onlyWrong answer — click to see why▾
Why this is wrong here
AH only provides authentication and integrity, but does not encrypt the payload or the original header, failing to meet the requirement to encrypt all traffic.
★ When this WOULD be the correct answer
When the requirement is only to authenticate and ensure integrity of IP packets without encryption, such as in a scenario where data confidentiality is not needed but protection against tampering is required.
Why candidates choose this
Candidates may confuse AH with ESP, or think that AH provides encryption because it is part of IPsec, but AH only offers authentication, not encryption.
✗ESP onlyWrong answer — click to see why▾
Why this is wrong here
ESP only can be used in either transport or tunnel mode, but the question asks for the mode that encrypts the entire IP packet including the original header. ESP alone does not specify the mode; tunnel mode is required for full packet encryption.
★ When this WOULD be the correct answer
A question asking: 'Which IPsec protocol provides encryption but not authentication of the IP header?' would make ESP only correct, as AH provides authentication but not encryption.
Why candidates choose this
Candidates may confuse ESP with tunnel mode, thinking ESP inherently encrypts the entire packet, but ESP can operate in transport mode which only encrypts the payload.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The N10-009 exam often tests the distinction between Transport and Tunnel modes by asking which mode encrypts the entire packet, and candidates mistakenly choose Transport mode because they confuse 'encrypting the payload' with 'encrypting the entire packet', or they think AH provides encryption.
Detailed technical explanation
How to think about this question
In IPsec Tunnel mode, the entire original IP datagram (header and payload) is encrypted and encapsulated within a new IP packet with a new IP header, typically with ESP providing encryption and optional authentication. The new IP header contains the addresses of the VPN gateways, allowing the original packet to traverse the public internet securely. This mode is defined in RFC 4301 and is the standard for site-to-site VPNs, whereas Transport mode is more commonly used for end-to-end communications between hosts, such as in a remote access VPN scenario.
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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Tunnel mode — Tunnel mode is the correct choice because it encrypts the entire original IP packet, including the original header, and then encapsulates it within a new IP header. This is required for site-to-site VPNs where the original source and destination IP addresses must be hidden or protected, and the new header is used for routing between the two VPN gateways.
What should I do if I get this N10-009 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: Jun 11, 2026
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