SSCP Network and Communications Security Practice Question
A security engineer is configuring a site-to-site VPN between two branch offices using IPsec in tunnel mode. Which protocol provides both authentication and encryption of the entire original IP packet?
⚠ Common exam trap
SSCP often tests the AH vs. ESP distinction — the trap is selecting AH for 'authentication' when the question also requires encryption, which only ESP provides.
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) in tunnel mode
ESP (Encapsulating Security Payload) in tunnel mode encrypts and authenticates the entire original IP packet, then encapsulates it inside a new IP packet with new headers. This provides confidentiality, integrity, and origin authentication for the payload, making it the standard choice for site-to-site VPNs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
IKEv2 in transport mode
Why it's wrong here
IKEv2 negotiates security associations but does not itself encrypt payload traffic; transport mode also leaves the original IP header unencrypted, so the entire packet is not protected. It is tempting because IKEv2 is the correct protocol for establishing IPsec tunnels, but tunnel mode with ESP is what encrypts the whole original packet.
- ✓
ESP (Encapsulating Security Payload) in tunnel mode
Why this is correct
ESP in tunnel mode encapsulates the entire original IP packet and applies both encryption and authentication, satisfying the stem's dual requirement. AH provides authentication only, without confidentiality, so it cannot encrypt payloads. ESP's tunnel encapsulation also hides original source and destination addresses, which transport mode does not.
- ✗
L2TP in tunnel mode
Why it's wrong here
L2TP supplies no encryption or authentication itself; it relies on IPsec for both, so alone it cannot secure the tunnel. It is tempting because L2TP is commonly paired with IPsec in VPN deployments, and would be correct if the question asked which tunnelling protocol carries PPP sessions rather than which provides cryptographic protection.
- ✗
AH (Authentication Header) in tunnel mode
Why it's wrong here
AH provides integrity and authentication only; it does not encrypt payload, so the original IP packet's contents remain readable. It is tempting because AH authenticates the entire packet including the outer header, and would be correct if the requirement were authentication without confidentiality.
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
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Same concept, more angles
1 more way this is tested on SSCP
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. In IPsec VPNs, which protocol provides authentication and encryption of the entire IP packet, including the IP header, in tunnel mode?
hard- A.L2TP
- B.IKE
- ✓ C.ESP
- D.AH
Why C: ESP (Encapsulating Security Payload) is the IPsec protocol that provides both confidentiality (encryption) and authentication for the entire IP packet in tunnel mode. In tunnel mode, ESP encapsulates the original IP packet—including its header—inside a new IP packet, encrypting the payload and optionally authenticating it via HMAC. AH, by contrast, only provides authentication and integrity, not encryption. Therefore, ESP is the correct answer.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
This SSCP 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 SSCP exam.