SSCP Network and Communications Security Practice Question
This SSCP practice question tests your understanding of network and communications security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 company's internal network uses a /24 subnet and has a single firewall connecting to the internet. Employees report that they cannot access an external web server at 203.0.113.50. The firewall has a rule that allows outbound HTTP. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NAT is not configured for outbound traffic.
The firewall rule allows outbound HTTP, but without NAT configured, the internal hosts' private IP addresses (e.g., 192.168.1.x) are used as source addresses in packets sent to the external web server. The web server at 203.0.113.50 will see these private addresses as the source and attempt to reply to them, but private addresses are not routable on the public internet, so the return traffic never reaches the internal hosts. NAT (specifically source NAT or PAT) translates the private source IP to the firewall's public IP, enabling two-way communication.
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.
✗
The default gateway on the internal hosts is incorrect.
Why it's wrong here
If hosts can reach other internal resources, the gateway is likely correct.
✓
NAT is not configured for outbound traffic.
Why this is correct
Internal private IPs must be translated to a public IP for internet access.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
DNS resolution is failing for the server name.
Why it's wrong here
The user is accessing by IP, so DNS is not involved.
✗
An ACL is blocking the destination IP.
Why it's wrong here
The rule allows HTTP, so an ACL block is unlikely unless specifically configured.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a firewall rule allowing outbound HTTP is sufficient, forgetting that NAT is required to translate private source addresses to a routable public IP for return traffic to succeed.
Detailed technical explanation
How to think about this question
Under the hood, NAT (Network Address Translation) as defined in RFC 2663 and RFC 3022 is essential for translating private RFC 1918 addresses (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) to a public IP. Without NAT, the TCP three-way handshake fails because the SYN-ACK from the server is sent to the private IP, which is dropped by the first upstream router. In real-world scenarios, many firewalls default to 'no NAT' for outbound traffic unless explicitly configured, and this is a common misconfiguration during initial setup.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
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.
Network and Communications Security — This question tests Network and Communications Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NAT is not configured for outbound traffic. — The firewall rule allows outbound HTTP, but without NAT configured, the internal hosts' private IP addresses (e.g., 192.168.1.x) are used as source addresses in packets sent to the external web server. The web server at 203.0.113.50 will see these private addresses as the source and attempt to reply to them, but private addresses are not routable on the public internet, so the return traffic never reaches the internal hosts. NAT (specifically source NAT or PAT) translates the private source IP to the firewall's public IP, enabling two-way communication.
What should I do if I get this SSCP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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