- A
Check the NAT rule for correct interface assignment.
Why wrong: The NAT rule is already configured and internal access works, so NAT is likely functioning.
- B
Check the DNS proxy configuration on the firewall.
Why wrong: DNS proxy would affect name resolution, but the issue could persist even with DNS if the web traffic is blocked by policy.
- C
Review the security policy to ensure traffic from the internal zone to the external zone is allowed.
If internal access works but external website access fails, the most likely cause is a security policy blocking web traffic. Checking the security policy is the logical first step.
- D
Verify that the default route is active by checking the routing table.
Why wrong: Internal access working indicates routing is likely correct.
PCNSE Troubleshoot Practice Question
This PCNSE practice question tests your understanding of troubleshoot. 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 security administrator reports that they can ping and access internal resources, but cannot access any external websites. The firewall is configured with a default route pointing to the internet router, and the NAT policy includes a source NAT rule for the internal subnet. Which step should the administrator take first to troubleshoot this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Review the security policy to ensure traffic from the internal zone to the external zone is allowed.
Option C is correct because if internal access works but external website access fails, the most likely cause is a security policy blocking web traffic. The default route and NAT appear configured, so checking the security policy is the logical first step. Option A is wrong because DNS proxy would affect name resolution, but the issue could persist even with DNS if the web traffic is blocked by policy. Option B is wrong because internal access working indicates routing is likely correct. Option D is wrong because the NAT rule is already configured and internal access works, so NAT is likely functioning.
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 NAT rule for correct interface assignment.
Why it's wrong here
The NAT rule is already configured and internal access works, so NAT is likely functioning.
- ✗
Check the DNS proxy configuration on the firewall.
Why it's wrong here
DNS proxy would affect name resolution, but the issue could persist even with DNS if the web traffic is blocked by policy.
- ✓
Review the security policy to ensure traffic from the internal zone to the external zone is allowed.
Why this is correct
If internal access works but external website access fails, the most likely cause is a security policy blocking web traffic. Checking the security policy is the logical first step.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
- ✗
Verify that the default route is active by checking the routing table.
Why it's wrong here
Internal access working indicates routing is likely correct.
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.
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FAQ
Questions learners often ask
What does this PCNSE question test?
Troubleshoot — This question tests Troubleshoot — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Review the security policy to ensure traffic from the internal zone to the external zone is allowed. — Option C is correct because if internal access works but external website access fails, the most likely cause is a security policy blocking web traffic. The default route and NAT appear configured, so checking the security policy is the logical first step. Option A is wrong because DNS proxy would affect name resolution, but the issue could persist even with DNS if the web traffic is blocked by policy. Option B is wrong because internal access working indicates routing is likely correct. Option D is wrong because the NAT rule is already configured and internal access works, so NAT is likely functioning.
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.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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Last reviewed: Jun 24, 2026
This PCNSE practice question is part of Courseiva's free Palo Alto Networks 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 PCNSE exam.
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