- A
ESP (Encapsulating Security Payload)
ESP provides both encryption and authentication.
- B
IKE (Internet Key Exchange)
Why wrong: IKE handles key exchange, not packet protection.
- C
ISAKMP
Why wrong: ISAKMP is a framework for key exchange, not a protocol for encrypting packets.
- D
AH (Authentication Header)
Why wrong: AH provides integrity and authentication but no encryption.
Question 270 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and 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 network engineer is configuring an IPsec VPN in tunnel mode. Which IPsec protocol provides both authentication and encryption of the entire IP packet?
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 (Encapsulating Security Payload)
ESP (Encapsulating Security Payload) in tunnel mode provides both authentication and encryption for the entire original IP packet, including the original header and payload. It encapsulates the packet with a new IP header and ESP trailer, ensuring confidentiality via encryption and integrity via authentication. This makes it the correct choice for a VPN requiring both security services.
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.
- ✓
ESP (Encapsulating Security Payload)
Why this is correct
ESP provides both encryption and authentication.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
IKE (Internet Key Exchange)
Why it's wrong here
IKE handles key exchange, not packet protection.
- ✗
ISAKMP
Why it's wrong here
ISAKMP is a framework for key exchange, not a protocol for encrypting packets.
- ✗
AH (Authentication Header)
Why it's wrong here
AH provides integrity and authentication but no encryption.
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 can provide encryption because it offers authentication, but AH never encrypts data—it only provides integrity and origin authentication, making ESP the only correct choice for both authentication and encryption.
Detailed technical explanation
How to think about this question
In tunnel mode, ESP encrypts the entire inner IP packet (including its header) and appends a new outer IP header, ESP header, and ESP trailer. The authentication covers the ESP header, payload, and trailer, but not the outer IP header (unless combined with AH). This mode is commonly used for site-to-site VPNs, where the original packet is fully protected between gateways, and the outer header is used for routing across the public 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 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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Communication and Network Security — study guide chapter
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ESP (Encapsulating Security Payload) — ESP (Encapsulating Security Payload) in tunnel mode provides both authentication and encryption for the entire original IP packet, including the original header and payload. It encapsulates the packet with a new IP header and ESP trailer, ensuring confidentiality via encryption and integrity via authentication. This makes it the correct choice for a VPN requiring both security services.
What should I do if I get this CISSP 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
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Last reviewed: Jul 4, 2026
This CISSP 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 CISSP exam.
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