- A
L2TP/IPsec with pre-shared keys
Why wrong: L2TP/IPsec can use certificates for mutual auth, but the question specifies no pre-shared keys; using PSK is common but weak; also perfect forward secrecy depends on IKE configuration, not guaranteed.
- B
PPTP with MS-CHAPv2
Why wrong: PPTP is deprecated and insecure; MS-CHAPv2 is vulnerable to brute-force attacks and does not provide perfect forward secrecy.
- C
WireGuard
WireGuard meets all requirements: ECC key exchange provides perfect forward secrecy, public-key authentication is mutual, and no PSK is needed.
- D
IPsec with IKEv2 using pre-shared keys
Why wrong: Pre-shared keys can be brute-forced and do not provide perfect forward secrecy by default; mutual authentication is possible but PSK is not ideal.
Question 790 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security engineer is evaluating VPN protocols for a remote access solution. The requirements are: strong encryption with perfect forward secrecy, support for mutual authentication, and no reliance on pre-shared keys that could be brute-forced. Which protocol best meets these requirements?
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
✓
WireGuard
WireGuard is the correct choice because it uses modern cryptographic primitives (Curve25519, ChaCha20, Poly1305, BLAKE2s) that inherently provide perfect forward secrecy via ephemeral Diffie-Hellman key exchanges, supports mutual authentication through public-key-based handshakes, and eliminates pre-shared keys as the sole authentication factor—though an optional PSK can be added for post-quantum resistance, it is not required and does not weaken security if omitted.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
L2TP/IPsec with pre-shared keys
Why it's wrong here
L2TP/IPsec can use certificates for mutual auth, but the question specifies no pre-shared keys; using PSK is common but weak; also perfect forward secrecy depends on IKE configuration, not guaranteed.
- ✗
PPTP with MS-CHAPv2
Why it's wrong here
PPTP is deprecated and insecure; MS-CHAPv2 is vulnerable to brute-force attacks and does not provide perfect forward secrecy.
- ✓
WireGuard
Why this is correct
WireGuard meets all requirements: ECC key exchange provides perfect forward secrecy, public-key authentication is mutual, and no PSK is needed.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
IPsec with IKEv2 using pre-shared keys
Why it's wrong here
Pre-shared keys can be brute-forced and do not provide perfect forward secrecy by default; mutual authentication is possible but PSK is not ideal.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that IPsec with IKEv2 is always secure regardless of authentication method, but the trap here is that pre-shared keys (even with IKEv2) violate the 'no reliance on pre-shared keys' requirement and can be brute-forced if weak, whereas WireGuard's public-key-based mutual authentication avoids this vulnerability entirely.
Detailed technical explanation
How to think about this question
WireGuard operates at Layer 3 using a Noise protocol framework (specifically Noise_IKpsk2) for key exchange, where each peer generates ephemeral keys per session to achieve perfect forward secrecy; the handshake is a single round-trip (1-RTT) that simultaneously authenticates both parties using long-term public keys and derives session keys without exposing static keys to offline brute-force attacks. In real-world deployments, WireGuard's minimal codebase (~4,000 lines) reduces attack surface compared to IPsec's complex IKEv2 stack, and its integration into the Linux kernel (since 5.6) ensures low-latency performance ideal for remote access VPNs.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: WireGuard — WireGuard is the correct choice because it uses modern cryptographic primitives (Curve25519, ChaCha20, Poly1305, BLAKE2s) that inherently provide perfect forward secrecy via ephemeral Diffie-Hellman key exchanges, supports mutual authentication through public-key-based handshakes, and eliminates pre-shared keys as the sole authentication factor—though an optional PSK can be added for post-quantum resistance, it is not required and does not weaken security if omitted.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This CISSP 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 CISSP exam.
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