- A
AH in tunnel mode
Why wrong: AH provides authentication but no encryption, failing the encryption requirement.
- B
AH in transport mode
Why wrong: AH lacks encryption and transport mode is inappropriate for site-to-site.
- C
ESP in tunnel mode
ESP in tunnel mode encrypts and authenticates the entire packet, suitable for site-to-site VPNs.
- D
ESP in transport mode
Why wrong: Transport mode is for end-to-end communication, not for gateway-to-gateway VPNs.
Question 781 of 1,000
hardMultiple ChoiceObjective-mapped
IPsec ESP in Tunnel Mode for Secure WAN Links
This SSCP practice question tests your understanding of sscp exam topics. 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 network engineer is designing a secure WAN link between two offices using IPsec VPN. The company requires encryption of all traffic, authentication of both endpoints, and protection against replay attacks. Which combination of IPsec protocols and modes should be used?
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
✓
ESP in tunnel mode
ESP in tunnel mode encrypts and authenticates the entire original IP packet, providing confidentiality, integrity, and authentication for the entire payload. It also includes sequence numbers to protect against replay attacks, making it the correct choice for a secure WAN link between two offices.
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.
- ✗
AH in tunnel mode
Why it's wrong here
AH provides authentication but no encryption, failing the encryption requirement.
- ✗
AH in transport mode
Why it's wrong here
AH lacks encryption and transport mode is inappropriate for site-to-site.
- ✓
ESP in tunnel mode
Why this is correct
ESP in tunnel mode encrypts and authenticates the entire packet, suitable for site-to-site VPNs.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
ESP in transport mode
Why it's wrong here
Transport mode is for end-to-end communication, not for gateway-to-gateway VPNs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse AH with ESP, assuming AH provides encryption, or they incorrectly choose transport mode for site-to-site VPNs because they focus on endpoint authentication rather than the need to encapsulate the entire original packet for network-to-network communication.
Detailed technical explanation
How to think about this question
ESP in tunnel mode creates a new outer IP header and encrypts the entire original IP packet, including its header, then appends an ESP trailer and authentication data. The sequence number in the ESP header is used for replay protection, and the combination of encryption (e.g., AES) and HMAC (e.g., SHA-256) ensures both confidentiality and integrity. In real-world deployments, this is commonly configured with IKEv2 for key exchange and can be set using commands like 'crypto ipsec transform-set' in Cisco IOS.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
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.
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FAQ
Questions learners often ask
What does this SSCP question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: ESP in tunnel mode — ESP in tunnel mode encrypts and authenticates the entire original IP packet, providing confidentiality, integrity, and authentication for the entire payload. It also includes sequence numbers to protect against replay attacks, making it the correct choice for a secure WAN link between two offices.
What should I do if I get this SSCP 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: Jun 11, 2026
This SSCP practice question is part of Courseiva's free ISC2 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 SSCP exam.
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