The answer is that the firewall is not stateful and does not automatically allow return traffic; a separate rule is needed. This is because a stateless firewall evaluates each packet in isolation based solely on source and destination IP addresses and ports, without tracking the state of a connection. When users in 10.2.2.0/24 initiate a new session to the web server in 10.1.1.0/24, the firewall sees the source and destination reversed from the existing rule and drops the traffic, as no rule permits that direction. On the ISC2 Certified in Cybersecurity CC exam, this tests your understanding of the fundamental difference between stateful and stateless firewalls—a common trap is assuming a single rule covers both directions. Remember the memory tip: “Stateless sees each packet as a stranger; stateful remembers who it just shook hands with.”
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network 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 network administrator is troubleshooting a connectivity issue between two segments separated by a firewall. The firewall rule allows traffic from 10.1.1.0/24 to 10.2.2.0/24 on TCP 443. Users in 10.1.1.0/24 can access the web server at 10.2.2.10, but users in 10.2.2.0/24 cannot access a web server in 10.1.1.0/24. 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
✓
The firewall is not stateful and does not automatically allow return traffic; a separate rule is needed.
The firewall rule only permits traffic from 10.1.1.0/24 to 10.2.2.0/24 on TCP 443. When users in 10.2.2.0/24 initiate a connection to the web server in 10.1.1.0/24, the firewall sees a new session that does not match the existing rule (source/destination reversed). If the firewall is not stateful, it will not automatically allow the return traffic for the reverse direction, and no separate rule exists to permit that traffic, causing the connectivity failure.
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 web server in 10.1.1.0 is blocking the IP range of 10.2.2.0/24.
Why it's wrong here
If the server were blocking, users in 10.1.1.0 would also be affected, but they can access it.
✗
The firewall rule is incorrectly applied to the wrong interface.
Why it's wrong here
The rule is applied correctly as traffic from 10.1.1.0/24 to 10.2.2.0/24 works, so interface assignment is likely correct.
✗
The subnet masks are misconfigured, causing routing issues.
Why it's wrong here
Subnet mask issues would cause bidirectional connectivity problems, not one-way.
✓
The firewall is not stateful and does not automatically allow return traffic; a separate rule is needed.
Why this is correct
Without stateful inspection, each direction requires an explicit rule. The existing rule only covers one direction.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that a single firewall rule allowing traffic in one direction automatically permits the return traffic, but in stateless firewalls or when stateful inspection is disabled, you must explicitly create a rule for the reverse direction.
Detailed technical explanation
How to think about this question
Stateful firewalls track connection state and automatically permit return traffic for established sessions, but a stateless firewall (or a stateful firewall with a strict rule set) requires explicit rules for each direction. In this scenario, the firewall is likely stateless or configured to not inspect state, so the return traffic from 10.1.1.0/24 to 10.2.2.0/24 is dropped because no rule matches the source (10.2.2.0/24) and destination (10.1.1.0/24). A real-world example is using an ACL on a router or a packet-filtering firewall without stateful inspection, where you must add a permit rule for the reverse direction.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall is not stateful and does not automatically allow return traffic; a separate rule is needed. — The firewall rule only permits traffic from 10.1.1.0/24 to 10.2.2.0/24 on TCP 443. When users in 10.2.2.0/24 initiate a connection to the web server in 10.1.1.0/24, the firewall sees a new session that does not match the existing rule (source/destination reversed). If the firewall is not stateful, it will not automatically allow the return traffic for the reverse direction, and no separate rule exists to permit that traffic, causing the connectivity failure.
What should I do if I get this CC 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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