Security Policy Zone Mismatch — Why Traffic Fails to Reach DMZ Server
This PCNSE practice question tests your understanding of deploy and configure firewalls. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Exhibit
admin@PA-5050> show running security-policy
rulebase security rules {
"Permit-Web" {
from "trust"
to "untrust"
source "10.0.0.0/8"
destination "any"
application "web-browsing"
action "allow"
}
}
Refer to the exhibit. A user in the 10.0.0.0/8 network is unable to access a web server at 172.16.1.10 which is in the DMZ zone. The firewall's security policy is shown. What is the most likely reason for the failure?
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.
Exhibit
admin@PA-5050> show running security-policy
rulebase security rules {
"Permit-Web" {
from "trust"
to "untrust"
source "10.0.0.0/8"
destination "any"
application "web-browsing"
action "allow"
}
}
A
The source IP range 10.0.0.0/8 is misconfigured.
Why wrong: The source IP range 10.0.0.0/8 includes the user's IP, so this is not misconfigured. The failure is due to the destination zone mismatch.
B
The policy specifies the 'untrust' zone instead of the 'dmz' zone.
The policy's destination zone is 'untrust', but the web server is in the 'dmz' zone, so the traffic does not match this policy, causing the failure.
C
The policy is missing a 'permit' action.
Why wrong: The policy action is 'allow', so the policy is not missing a permit action.
D
The application 'web-browsing' is not the correct application for the traffic.
Why wrong: Web-browsing is the correct application for HTTP traffic, so this is not the cause of the failure.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy specifies the 'untrust' zone instead of the 'dmz' zone.
Option B is correct because the policy's destination zone is 'untrust', but the server is in the 'dmz' zone, so the traffic does not match this policy. Option A is incorrect because the source IP range 10.0.0.0/8 includes the user's IP, so it is not misconfigured. Option C is incorrect because the policy has an 'allow' action, so it is not missing a permit. Option D is incorrect because 'web-browsing' is the correct application for HTTP traffic.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 source IP range 10.0.0.0/8 is misconfigured.
Why it's wrong here
The source IP range 10.0.0.0/8 includes the user's IP, so this is not misconfigured. The failure is due to the destination zone mismatch.
✓
The policy specifies the 'untrust' zone instead of the 'dmz' zone.
Why this is correct
The policy's destination zone is 'untrust', but the web server is in the 'dmz' zone, so the traffic does not match this policy, causing the failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The policy is missing a 'permit' action.
Why it's wrong here
The policy action is 'allow', so the policy is not missing a permit action.
✗
The application 'web-browsing' is not the correct application for the traffic.
Why it's wrong here
Web-browsing is the correct application for HTTP traffic, so this is not the cause of the failure.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCNSE ACL questions on filtering logic and placement.
Deploy and Configure Firewalls — This question tests Deploy and Configure Firewalls — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The policy specifies the 'untrust' zone instead of the 'dmz' zone. — Option B is correct because the policy's destination zone is 'untrust', but the server is in the 'dmz' zone, so the traffic does not match this policy. Option A is incorrect because the source IP range 10.0.0.0/8 includes the user's IP, so it is not misconfigured. Option C is incorrect because the policy has an 'allow' action, so it is not missing a permit. Option D is incorrect because 'web-browsing' is the correct application for HTTP traffic.
What should I do if I get this PCNSE question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCNSE ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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