CAS-004 Security Engineering Practice Question
A security architect is designing a VPN that requires both authentication and encryption. Which IPsec protocol provides both services in a single protocol?
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 provides both encryption and optional authentication, while AH only provides authentication without encryption.
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 transport mode
Why it's wrong here
AH does not provide encryption.
- ✗
IKEv2
Why it's wrong here
IKEv2 is a key exchange protocol, not a security protocol.
- ✓
ESP in tunnel mode
Why this is correct
ESP offers both encryption and authentication, tunnel mode encapsulates the entire IP packet.
- ✗
AH in tunnel mode
Why it's wrong here
AH provides only authentication, 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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.