156-215.81.20 VPN Basics Practice Question
Refer to the exhibit.
[VPN]
Community: HQ-Branch-Star Tunnel type: Permanent Tunnel Status: Down (Reason: No valid SA found)
An administrator reviews the VPN status output shown above for a permanent tunnel in a Star community. Despite the permanent tunnel setting, the tunnel remains down. What is the most likely cause of this behavior?
⚠ Common exam trap
Candidates assume that enabling a 'Permanent Tunnel' setting automatically fixes routing or NAT issues, ignoring the fact that underlying network paths must first be functional for negotiations to succeed.
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
✓
The underlying routing table or NAT configuration prevents the gateway from reaching the peer IP address.
Permanent tunnels instruct the Check Point gateway to aggressively maintain active IPsec security associations even when no actual user traffic traverses the link. However, if underlying routing, NAT rules, or Phase 1 authentication parameters are misconfigured, the gateway's recurring negotiation attempts will continuously fail, leaving the status as down with no valid SA found.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Traffic has been idle across the VPN tunnel for longer than the configured rekey interval timer.
Why it's wrong here
Permanent tunnel configurations are specifically designed to ignore traffic idleness by continuously re-establishing security associations before they expire. Idleness alone will not cause a permanent tunnel to remain down if cryptographic parameters and routing paths are healthy.
- ✓
The underlying routing table or NAT configuration prevents the gateway from reaching the peer IP address.
Why this is correct
If the gateway cannot physically reach the peer IP address due to routing blackholes or misconfigured Hide NAT rules, all initiation attempts fail. Without IP reachability, the permanent tunnel mechanism cannot establish the initial ISAKMP socket connection.
- ✗
SmartConsole is experiencing a database synchronization delay preventing policy push operations.
Why it's wrong here
A SmartConsole database synchronisation delay would block policy installation, not produce 'No valid SA found' on an established permanent tunnel. Synchronisation issues matter when policy pushes fail or management objects diverge, which is a management-plane scenario, not IKE Phase 2 negotiation failure.
- ✗
The Security Management Server has revoked the internal certificate of the center gateway object.
Why it's wrong here
Revoking the centre gateway's internal certificate would break certificate-based authentication for the whole community, yet the exhibit shows a single tunnel lacking a valid SA. Certificate revocation is the right diagnosis when authentication itself fails, not when Phase 2 SA negotiation cannot complete.
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.
About these practice questions
This 156-215.81.20 question is part of Courseiva's 210-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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 156-215.81.20 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 156-215.81.20 exam.