PCNSA Policy Evaluation and Management Practice Question
Exhibit
Refer to the exhibit. admin@PA-500> show running security-policy name from to source destination application action ------------------------------------------------------------------------------------------------------------------ 1 allow-web trust untrust 192.168.1.0/24 any web-browsing allow 2 block-social trust untrust 192.168.1.0/24 any social-networking deny 3 allow-all trust untrust any any any allow
A user at 192.168.1.10 attempts to access a social networking site (application: social-networking). Based on the exhibit, what will the firewall do?
⚠ Common exam trap
Watch out — candidates often assume a more permissive rule later in the policy (like rule 3 allowing all traffic) will override an earlier deny rule, but the firewall's first-match logic means the deny rule takes precedence.
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
✓
Deny the traffic because rule 2 matches and denies social-networking.
The firewall evaluates rules in order from top to bottom. Rule 2 explicitly denies the application 'social-networking', and since the user at 192.168.1.10 is attempting to access a social-networking site, rule 2 matches before any subsequent rule. Therefore, the traffic is denied. Option D is correct because rule 2 matches and denies the traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Allow the traffic because rule 1 matches and allows all web traffic.
Why it's wrong here
Rule 1 matches the source zone and address but its application is web-browsing, not social-networking; PAN-OS matches on application, so rule 1 does not apply. An allow-web-browsing rule would permit traffic when the session's App-ID resolves to web-browsing.
- ✗
Allow the traffic because rule 3 allows all traffic.
Why it's wrong here
Rule 3's allow-all sits below the social-networking deny, and PAN-OS evaluates security rules top-down, stopping at the first match, so the deny takes effect. An allow-all rule would permit the traffic only if it preceded the deny.
- ✗
Deny the traffic because no rule allows social-networking.
Why it's wrong here
The exhibit's rules are evaluated in order, and a later rule explicitly permits social-networking from 192.168.1.10; the firewall therefore allows the session rather than falling through to an implicit deny. Implicit deny applies only when no rule matches, which is not the case here.
- ✓
Deny the traffic because rule 2 matches and denies social-networking.
Why this is correct
Palo Alto Networks evaluates security rules top-down and stops at the first match. Rule 2 matches the source zone, address and social-networking application, and its action is deny, so the firewall blocks the session before any later allow rule is evaluated.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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