The answer is performing Network Address Translation (NAT). A network firewall enforces access control policies by filtering traffic based on Layer 3 IP addresses and Layer 4 port numbers, using stateless or stateful inspection to permit or deny packets according to predefined rules—such as allowing HTTP traffic on TCP port 80 from a specific source IP. This core security mechanism segments networks and blocks unauthorized access, making NAT a secondary but common function that hides internal IP addresses. On the Systems Security Certified Practitioner SSCP exam, this tests your understanding of firewall functions as part of access control and network security domains; a common trap is confusing NAT with the firewall’s primary filtering role, so remember that while NAT is a function, the firewall’s main job is packet filtering. Memory tip: think “NAT hides, firewall decides.”
SSCP Network and Communications Security Practice Question
This SSCP practice question tests your understanding of network and communications security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which TWO of the following are functions of a network firewall?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Filtering traffic based on IP addresses and ports
Option B is correct because a network firewall's primary function is to enforce access control policies by filtering traffic based on Layer 3 (IP addresses) and Layer 4 (ports) information. This stateless or stateful inspection allows the firewall to permit or deny packets according to rules, such as allowing HTTP traffic (TCP port 80) from a specific source IP. This is a core security mechanism to segment networks and block unauthorized access.
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.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse optional features (like NAT or DHCP) with core firewall functions, or they mistake DNS resolution for a firewall capability, when the SSCP exam expects you to know that filtering based on IP/port is the fundamental purpose.
Detailed technical explanation
How to think about this question
Firewalls use packet filtering rules based on the 5-tuple (source IP, destination IP, source port, destination port, protocol) to make allow/deny decisions. Stateful firewalls maintain a connection table to track TCP handshakes and session states, enabling them to permit return traffic dynamically while blocking unsolicited inbound packets. In contrast, NAT (Network Address Translation) modifies IP addresses in packet headers, often used to map private RFC 1918 addresses to a public IP, and is a common firewall feature but not a filtering function.
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: Filtering traffic based on IP addresses and ports — Option B is correct because a network firewall's primary function is to enforce access control policies by filtering traffic based on Layer 3 (IP addresses) and Layer 4 (ports) information. This stateless or stateful inspection allows the firewall to permit or deny packets according to rules, such as allowing HTTP traffic (TCP port 80) from a specific source IP. This is a core security mechanism to segment networks and block unauthorized access.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which of the following is a primary function of a firewall?
easy
✓ A.Filter traffic based on rules
B.Assign IP addresses
C.Encrypt network traffic
D.Detect malware on endpoints
Why A: A firewall's primary function is to filter network traffic based on a defined set of security rules, such as source/destination IP addresses, ports, and protocols. It operates at the network layer (or higher) to permit or deny packets, acting as a barrier between trusted and untrusted networks. This rule-based filtering is the core mechanism that enforces access control policies.
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This SSCP practice question is part of Courseiva's free ISC2 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 SSCP exam.
Question Discussion
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