156-215.81.20 VPN Basics Practice Question
Which security feature is enabled by default in Check Point VPN communities to protect against replay attacks?
⚠ Common exam trap
Exam takers often look for complex manual rule configurations or cryptographic algorithms, missing that robust anti-replay defense mechanisms are simply enabled by default.
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
✓
Anti-Replay Protection
Anti-replay protection is a standard feature of the IPsec suite. It uses a sliding window protocol to track sequence numbers of incoming packets. If a packet arrives with a sequence number that has already been processed or is too old, the gateway drops it. This prevents an attacker from capturing encrypted packets and re-sending them later to cause unauthorized actions or service disruption on the internal network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Anti-Replay Protection
Why this is correct
Anti-Replay Protection is a core IPsec feature that tracks sequence numbers of packets within a tunnel. It ensures that every packet is unique and processed only once, preventing an attacker from capturing valid traffic and re-injecting it into the network to spoof authorized sessions or disrupt operations.
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IKE Aggressive Mode
Why it's wrong here
IKE Aggressive Mode is a less secure version of IKE Phase 1 that transmits identities in the clear. It is generally discouraged in production environments and is not a security feature designed to protect against replay attacks; in fact, it is considered a legacy risk factor.
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VPN Compression
Why it's wrong here
Compression is intended to reduce the size of the data payload for better bandwidth utilization. It does not provide security against replay attacks. In fact, compression can sometimes introduce side-channel vulnerabilities, which is why it is frequently disabled in modern, high-performance secure VPN configurations.
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Dynamic Routing over VPN
Why it's wrong here
Dynamic routing (like OSPF or BGP) over a VPN tunnel allows for automated topology updates and failover but provides no protection against replay attacks. It operates at the network layer to manage connectivity, whereas replay protection is a cryptographic mechanism handled by the IPsec ESP/AH protocol stack.
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
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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 156-215.81.20 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.