This PCNSE practice question tests your understanding of troubleshoot. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 engineer notices that traffic from a specific subnet is being dropped by the firewall. The traffic log shows 'drop' with reason 'policy deny'. The engineer checks the security policy and confirms there is an allow rule for that subnet. What should be checked next?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the rule order and ensure the allow rule is above any deny rules.
The correct answer is A because if the allow rule is not above a deny rule, the deny rule will match first.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Check the application override.
Why it's wrong here
Application override affects application identification but not policy matching directly.
✗
Check the QoS policy.
Why it's wrong here
QoS policy shapes traffic but does not deny it; a policy deny is from security rules.
✓
Check the rule order and ensure the allow rule is above any deny rules.
Why this is correct
A rule order issue is the most common cause when a policy deny occurs despite an allow rule existing.
NAT policy does not cause a policy deny; it translates addresses but does not affect policy matching.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNSE subnetting questions on CIDR, address ranges, and subnet selection.
Troubleshoot — This question tests Troubleshoot — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check the rule order and ensure the allow rule is above any deny rules. — The correct answer is A because if the allow rule is not above a deny rule, the deny rule will match first.
What should I do if I get this PCNSE question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNSE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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