SSCP Network and Communications Security Practice Question
An organization is setting up a site-to-site VPN between two branch offices. They require encryption of the entire IP packet, including the original IP header, and plan to use IPsec. Which mode should they configure?
⚠ Common exam trap
The trap is confusing IPsec modes (transport vs. tunnel) with protocols (ESP vs. AH). Candidates may select ESP or AH thinking they are modes, but the question specifically asks for the mode that encrypts the entire IP packet, which is tunnel mode.
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
✓
Tunnel mode
Tunnel mode in IPsec encapsulates the entire original IP packet, including the original IP header, within a new IP packet with a new IP header. This provides confidentiality and integrity for the entire packet and is typically used for site-to-site VPNs between gateways. Transport mode only encrypts the payload, leaving the original IP header intact, which does not meet the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Transport mode
Why it's wrong here
Transport mode encrypts only the payload; the original IP header remains unencrypted and is used for routing, so the entire packet is not protected. It is tempting because it is the default IPsec mode, but it would be correct for host-to-host traffic between two endpoints, not a gateway site-to-site tunnel.
- ✓
Tunnel mode
Why this is correct
Tunnel mode encapsulates the entire original IP packet inside a new IPsec packet, encrypting the original header as required. This satisfies the stem's whole-packet encryption constraint, whereas transport mode encrypts only the payload and leaves the original IP header intact.
- ✗
ESP mode
Why it's wrong here
ESP is a protocol, not a mode; it supplies confidentiality for the payload but does not by itself encrypt the original IP header, which requires tunnel mode. It is tempting because ESP is the encryption component of IPsec, but it would be correct when only payload confidentiality is required.
- ✗
AH mode
Why it's wrong here
AH provides authentication and integrity only; it does not encrypt the packet, so confidentiality of the entire IP packet is unmet. It is tempting because AH is an IPsec protocol operating in transport or tunnel mode, but the requirement for encryption means ESP, not AH, must be selected.
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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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.