This PCNSE practice question tests your understanding of secure access and vpn. 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 small company has two sites connected by a policy-based IPsec VPN. Users at Site B report they cannot reach a server at Site A with IP 10.1.1.100. The firewall administrator checks the VPN monitor and sees the tunnel is active and IKE SAs are up. From the Site B firewall, a ping to 10.1.1.100 succeeds. However, a user on a PC (192.168.50.10) behind the Site B firewall cannot ping 10.1.1.100. The security policy on the Site B firewall allows traffic from trust to VPN zones. What is the most likely cause of the issue?
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 security policy on Site B does not include the user subnet as a source VPN zone traffic
Option B is correct because the tunnel is policy-based and needs a security policy that includes the user subnet. Even though a general rule exists, it may not match the specific source. Option A is incorrect because the tunnel is up. Option C is incorrect because ping from firewall works. Option D is incorrect because routing is fine since the firewall can reach the destination.
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.
✓
The security policy on Site B does not include the user subnet as a source VPN zone traffic
Why this is correct
The policy must have the correct source zone (trust) and destination zone (VPN) and include the user subnet.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Proxy ID mismatch would prevent phase 2, but the tunnel is established.
✗
The Site A firewall has a route missing for the Site B user subnet
Why it's wrong here
The firewall can reach the server, so routing is fine.
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.
Secure Access and VPN — This question tests Secure Access and VPN — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The security policy on Site B does not include the user subnet as a source VPN zone traffic — Option B is correct because the tunnel is policy-based and needs a security policy that includes the user subnet. Even though a general rule exists, it may not match the specific source. Option A is incorrect because the tunnel is up. Option C is incorrect because ping from firewall works. Option D is incorrect because routing is fine since the firewall can reach the destination.
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: "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?
CIDR notation defines the prefix length.
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Question Discussion
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