CAS-004 Security Engineering Practice Question
An organization is implementing IPsec VPNs between sites. The security team wants to ensure data integrity and authentication but is less concerned about confidentiality for this particular link. Which IPsec protocol and mode should they use?
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
✓
AH in tunnel mode
AH provides authentication and integrity without encryption. Transport mode is used for end-to-end communication, while tunnel mode is for gateway-to-gateway. Since this is between sites (gateways), tunnel mode is appropriate. AH in transport mode is for host-to-host. ESP provides confidentiality. AH in tunnel mode is correct.
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 in tunnel mode
Why it's wrong here
ESP includes encryption, which is not required.
- ✓
AH in tunnel mode
Why this is correct
AH provides integrity and authentication without encryption; tunnel mode is for site-to-site VPNs.
- ✗
AH in transport mode
Why it's wrong here
Transport mode is host-to-host; for site-to-site, tunnel mode is needed.
- ✗
ESP in transport mode
Why it's wrong here
ESP provides encryption, which is not needed.
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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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.