CISSP Communication and Network Security Practice Question
A network engineer is configuring an IPsec VPN in tunnel mode. Which IPsec protocol provides both authentication and encryption of the entire IP packet?
⚠ Common exam trap
A common pitfall is thinking AH (Authentication Header) provides encryption because it offers authentication, but AH only ensures integrity and origin authentication—it does not encrypt. For both authentication and encryption, ESP must 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 (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.
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.
- ✗
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.
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.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
VPN
A VPN (Virtual Private Network) creates a secure, encrypted tunnel between your device and a remote server, protecting your data and hiding your online activity.
Key term
Encryption
Encryption is the process of converting readable data into a secret code to prevent unauthorized access.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.