CND Practice Question: Network Security Controls Protocols And Devices
A security analyst is troubleshooting an IPsec site-to-site VPN tunnel failure on a Linux-based StrongSwan gateway. The logs indicate an 'ESP packet decryption failed' error. Upon reviewing the security association parameters, the analyst notices a mismatch in the cryptographic checksum algorithm. Which IPsec protocol component is responsible for providing data integrity and authentication for the inner 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
✓
Encapsulating Security Payload (ESP)
The Encapsulating Security Payload (ESP) protocol provides origin authenticity, integrity, and confidentiality protection of packets. The Authentication Header (AH) provides integrity and authentication only, without confidentiality.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Security Association Database (SAD)
Why it's wrong here
The SAD stores the parameters of security associations, but it is a database of states rather than the transport protocol component itself.
- ✗
Authentication Header (AH)
Why it's wrong here
AH provides integrity and authentication for IP packets, but it does not provide encryption, which matches the decryption failure symptom.
- ✗
Internet Key Exchange (IKE)
Why it's wrong here
IKE is used for setting up a security association (SA) between two parties; it is not the protocol that handles data packet decryption during ongoing transmission.
- ✓
Encapsulating Security Payload (ESP)
Why this is correct
ESP provides integrity, authentication, and encryption services for IPsec, and its cryptographic parameters must match on both peers to avoid decryption failures.
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.
About these practice questions
One of 323 original CND practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official EC-Council exam blueprint
This CND practice question is part of Courseiva's free EC-Council 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 CND exam.