ISC2 CC Network Security Practice Question
A security engineer is deploying a new VPN solution for remote employees. The company requires that the VPN provide strong encryption, support for multiple users, and the ability to traverse NAT devices. Which VPN protocol should the engineer choose?
⚠ Common exam trap
The trap here is assuming that any VPN protocol with encryption is sufficient, but NAT traversal and multi-user support are critical for remote access.
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
✓
L2TP/IPsec
L2TP/IPsec provides strong encryption through IPsec, supports multiple users, and can traverse NAT with NAT-T. It is a widely supported standard for remote access VPNs. The other options either lack strong encryption (PPTP), are platform-specific (SSTP), or are not designed for remote access tunneling (IPsec transport mode).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
PPTP
Why it's wrong here
PPTP (Point-to-Point Tunneling Protocol) is outdated and has known security vulnerabilities, including weak authentication and encryption. It does not provide strong encryption and is not recommended for securing sensitive data. While it can traverse NAT, its security weaknesses make it unsuitable for this scenario.
- ✗
IPsec in transport mode
Why it's wrong here
IPsec in transport mode encrypts only the payload of IP packets, not the entire packet, and is typically used for end-to-end communication between hosts. It does not provide a tunnel for remote access VPNs and may have issues traversing NAT without additional configuration. It is not the best choice for a remote access VPN.
- ✓
L2TP/IPsec
Why this is correct
L2TP/IPsec combines L2TP for tunneling with IPsec for strong encryption and authentication. It supports multiple users and can traverse NAT devices when NAT-T (NAT Traversal) is enabled. This makes it a suitable choice for remote access VPNs requiring strong security and NAT compatibility.
- ✗
SSTP
Why it's wrong here
SSTP (Secure Socket Tunneling Protocol) is a Microsoft proprietary protocol that uses SSL/TLS for encryption. While it provides strong encryption and can traverse NAT, it is not as widely supported across different platforms as L2TP/IPsec. The scenario does not specify a Windows-only environment, so a more universally supported protocol is preferable.
Visual reference
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
Learn chapter
Wireless and Remote Access Security
Key term
Standard
A standard is an agreed-upon set of rules, guidelines, or specifications that ensure consistency, compatibility, and quality across IT products, services, and processes.
Key term
PPTP
PPTP is an outdated VPN protocol that encapsulates PPP frames in IP packets for secure remote access, but is now considered insecure.
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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 CC 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 CC exam.