20+ practice questions focused on Communication and Network Security — one of the most tested topics on the Certified Information Systems Security Professional CISSP exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Communication and Network Security PracticeA security engineer is troubleshooting a network where internal users can access internet websites but cannot reach the company's external VPN server (IP 203.0.113.50, UDP port 500). The firewall rule for VPN traffic is correctly configured. What is the most likely cause?
Explanation: Option D is correct because the symptom—internal users can reach internet websites but cannot reach the external VPN server—indicates a host-level issue rather than a network or firewall problem. Since the firewall rule for VPN traffic is correctly configured and other traffic flows normally, the most likely cause is that the VPN server itself is not listening on UDP port 500, which is the standard port for IPsec IKE (Internet Key Exchange) traffic. This could be due to a misconfiguration, service failure, or the server being configured to use a different port or protocol.
A network architect is designing a secure connection between two data centers across an untrusted WAN. The requirement is to encrypt all traffic and authenticate both endpoints. Which protocol should be used?
Explanation: IPsec tunnel mode is the correct choice because it encrypts the entire IP packet, including the original IP header, and encapsulates it within a new IP header for secure transport across an untrusted WAN. It also provides mutual authentication of both endpoints using IKE (Internet Key Exchange) with pre-shared keys or certificates, satisfying the requirement for encrypting all traffic and authenticating both data centers.
A network administrator notices that users in the accounting department can access the internet but are unable to access the internal payroll server (10.10.10.50). The firewall rule allows traffic from the accounting subnet (10.10.20.0/24) to the payroll server. What is the most likely issue?
Explanation: The most likely issue is that the payroll server's default gateway does not have a route back to the accounting subnet (10.10.20.0/24). Even if the firewall permits outbound traffic from the accounting subnet to the payroll server, the return traffic from the server must be routed back through the firewall or a router that knows how to reach 10.10.20.0/24. Without a return route, the server's response packets are dropped, causing a one-way communication failure.
A company uses WPA2-Enterprise with EAP-TLS for wireless access. An employee reports that a new laptop cannot connect to the wireless network, while older laptops work fine. The employee has installed the correct client certificate. What is the most likely cause?
Explanation: In WPA2-Enterprise with EAP-TLS, mutual authentication requires the client to validate the RADIUS server's certificate. If the new laptop does not trust the RADIUS server's certificate (e.g., its CA root certificate is missing or expired), the EAP-TLS handshake will fail, preventing connection. Older laptops likely have the necessary root CA installed, while the new laptop does not.
A network engineer is configuring a firewall to allow HTTP traffic from the internet to a web server (10.0.0.10). The firewall has three interfaces: outside (ISP), DMZ (10.0.0.0/24), and inside (192.168.1.0/24). The web server is in the DMZ. Which rule is correct?
Explanation: Option B is correct because HTTP traffic from the internet arrives on the outside interface, and the firewall rule must match the source interface (Outside), allow any source IP, and specify the destination IP (10.0.0.10) and port 80. This permits inbound web traffic to the DMZ web server while maintaining security boundaries.
+15 more Communication and Network Security questions available
Practice all Communication and Network Security questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Communication and Network Security. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Communication and Network Security questions on the CISSP frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Communication and Network Security is tested as part of the Certified Information Systems Security Professional CISSP blueprint. Practicing with targeted Communication and Network Security questions ensures you can handle any format or difficulty that appears.
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Difficulty is subjective, but Communication and Network Security is a high-priority exam concept tested in multiple ways — direct recall, scenario analysis, and command-output interpretation. Consistent practice is the best way to build confidence.
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