- A
IKE (Internet Key Exchange)
Why wrong: IKE is used for key exchange, not data encryption.
- B
ISAKMP (Internet Security Association and Key Management Protocol)
Why wrong: ISAKMP is a framework for key exchange, not for data encryption.
- C
ESP (Encapsulating Security Payload)
ESP offers both encryption and authentication; in transport mode, it encrypts the payload only.
- D
AH (Authentication Header)
Why wrong: AH provides integrity and authentication but no encryption.
Question 892 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.
In IPsec, which protocol provides both authentication and encryption for the packet payload, but does not encrypt the IP 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
✓
ESP (Encapsulating Security Payload)
ESP (Encapsulating Security Payload) provides both authentication and encryption for the packet payload, while leaving the IP header unencrypted. This allows intermediate routers to process the packet normally, as the header remains in plaintext, but the payload is protected for confidentiality and integrity.
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.
- ✗
IKE (Internet Key Exchange)
Why it's wrong here
IKE is used for key exchange, not data encryption.
- ✗
ISAKMP (Internet Security Association and Key Management Protocol)
Why it's wrong here
ISAKMP is a framework for key exchange, not for data encryption.
- ✓
ESP (Encapsulating Security Payload)
Why this is correct
ESP offers both encryption and authentication; in transport mode, it encrypts the payload only.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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
Cisco often tests the distinction between ESP and AH by emphasizing that AH authenticates the entire packet (including the IP header) but provides no encryption, while ESP encrypts the payload but leaves the IP header unencrypted, leading candidates to mistakenly choose AH when encryption is required.
Detailed technical explanation
How to think about this question
ESP operates in two modes: transport mode (where only the payload is encrypted and authenticated) and tunnel mode (where the entire original IP packet is encapsulated and encrypted). In transport mode, the IP header is left unencrypted to maintain routing compatibility, while ESP adds a header and trailer to protect the payload. A subtle behavior is that ESP's authentication covers only the payload and ESP header, not the IP header, which differs from AH's coverage of the entire packet.
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 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) provides both authentication and encryption for the packet payload, while leaving the IP header unencrypted. This allows intermediate routers to process the packet normally, as the header remains in plaintext, but the payload is protected for confidentiality and integrity.
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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