The answer is Rule 2, the deny-all-from-trust-to-untrust rule, because PAN-OS evaluates security rules in top-down order and matches the first rule where all conditions are true. In this scenario, Rule 1 specifies the application HTTP, but the traffic is HTTPS (application ssl), so Rule 1 is skipped. Rule 2 then matches because it applies to any application from the 10.0.0.0/8 source zone (trust) to the destination zone (untrust), denying the connection before reaching Rule 3, which only matches DNS. On the PCNSA exam, this tests your understanding of rule evaluation order and application-based matching—a common trap is assuming a broad rule like “deny all” is only a last resort, but it will match immediately if earlier rules do not apply. Remember: PAN-OS reads rules from top to bottom like a checklist; if a rule’s source, destination, and application all match, the action is taken, and no further rules are checked. A useful memory tip is “first match wins, so order your specifics before your generals.”
PCNSA Securing Traffic Practice Question
This PCNSA practice question tests your understanding of securing traffic. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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
Refer to the exhibit.
admin@PA-500> show running security-policy
Rules:
1. name: allow-http-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: http
action: allow
2. name: deny-all-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: any
action: deny
3. name: allow-dns-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: dns
action: allow
Note: There are no other security rules.
A user at source IP 10.1.1.1 initiates an HTTPS connection to a web server on the internet. Which rule will the traffic match?
Refer to the exhibit.
admin@PA-500> show running security-policy
Rules:
1. name: allow-http-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: http
action: allow
2. name: deny-all-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: any
action: deny
3. name: allow-dns-from-trust-to-untrust
source: 10.0.0.0/8
destination: any
application: dns
action: allow
Note: There are no other security rules.
A
Rule 1: allow-http-from-trust-to-untrust (allow)
Why wrong: Rule 1 only matches HTTP, not HTTPS.
B
Rule 3: allow-dns-from-trust-to-untrust (allow)
Why wrong: Rule 3 only matches DNS.
C
Rule 2: deny-all-from-trust-to-untrust (deny)
Since HTTPS is not HTTP, rule 1 fails; rule 2 matches any application and denies.
D
No rule matches; implicit deny will block the traffic.
Why wrong: Rule 2 matches, so implicit deny is not reached.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rule 2: deny-all-from-trust-to-untrust (deny)
Option A is correct because rule 1 matches HTTP only; HTTPS is a different application (ssl). Rule 2 does not match because it is after rule 1? Actually the traffic hits rule 1 first, but since application is http and not ssl, rule 1 does not match. Then rule 2 matches because it applies to any application from 10.0.0.0/8, so it matches and denies the traffic. Rule 3 is for DNS only. So traffic will be denied by rule 2.
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.
Since HTTPS is not HTTP, rule 1 fails; rule 2 matches any application and denies.
Related concept
Standard ACLs match source addresses.
✗
No rule matches; implicit deny will block the traffic.
Why it's wrong here
Rule 2 matches, so implicit deny is not reached.
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 PCNSA ACL questions on filtering logic and placement.
Securing Traffic — This question tests Securing Traffic — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Rule 2: deny-all-from-trust-to-untrust (deny) — Option A is correct because rule 1 matches HTTP only; HTTPS is a different application (ssl). Rule 2 does not match because it is after rule 1? Actually the traffic hits rule 1 first, but since application is http and not ssl, rule 1 does not match. Then rule 2 matches because it applies to any application from 10.0.0.0/8, so it matches and denies the traffic. Rule 3 is for DNS only. So traffic will be denied by rule 2.
What should I do if I get this PCNSA 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 PCNSA ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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