156-315.81.20 Advanced VPN Design Practice Question
A security administrator is setting up a VPN community between two Check Point Security Gateways using IKEv2. The administrator wants to ensure that the gateways authenticate each other using certificates. What must be configured on both gateways to enable certificate-based authentication?
⚠ Common exam trap
Candidates often confuse authentication methods; pre-shared secrets are an alternative to certificates, not a requirement for certificate-based authentication.
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
✓
A valid certificate from a trusted Certificate Authority
To enable certificate-based authentication in an IKEv2 VPN community, each gateway must have a valid certificate issued by a trusted Certificate Authority. The gateways exchange these certificates during IKE negotiation and verify them against the trusted CA, providing mutual authentication without relying on pre-shared secrets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A valid certificate from a trusted Certificate Authority
Why this is correct
For certificate-based authentication, each gateway must have a certificate issued by a Certificate Authority (CA) that both gateways trust. The certificate contains the gateway's public key and identity, signed by the CA. During IKEv2 negotiation, the gateways exchange certificates and verify them against the trusted CA, establishing mutual authentication.
- ✗
A VPN tunnel interface
Why it's wrong here
A VPN tunnel interface (VTI) is used in Route-Based VPNs to direct traffic into the tunnel, but it is not related to authentication. Certificate-based authentication requires certificates, not a tunnel interface. The VTI is a routing construct, while certificates are used for identity verification during IKE negotiation.
- ✗
A shared secret key
Why it's wrong here
A shared secret key is another term for pre-shared secret, which is used for authentication but not certificate-based. Shared secrets are symmetric and must be configured identically on both gateways. They do not provide the scalability and non-repudiation that certificates offer. Therefore, this is not the correct choice for certificate-based authentication.
- ✗
Pre-shared secret
Why it's wrong here
A pre-shared secret is used for authentication in IKEv1 or IKEv2, but it is an alternative to certificates. If the administrator wants certificate-based authentication, a pre-shared secret is not used. Instead, each gateway must have a certificate issued by a trusted Certificate Authority. Pre-shared secrets are simpler but less secure for large deployments.
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.
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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 Check Point exam blueprint
This 156-315.81.20 practice question is part of Courseiva's free Check Point 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 156-315.81.20 exam.