PCNSA Policy Evaluation and Management Practice Question
A network administrator notices that traffic from a specific subnet is being denied even though there is a permit rule that matches the source and destination. The rulebase has over 500 rules. What is the most likely cause?
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
✓
A previous rule with a broader match is denying the traffic before reaching the permit rule.
In a firewall rulebase, rules are evaluated from top to bottom. If a previous rule with a broader match denies the traffic, it will be blocked before reaching the permit rule lower in the list. Option B is incorrect because the implicit deny is only at the end of the rulebase; there is no implicit deny earlier. Options A and D are unrelated to the scenario: asymmetric routing from destination NAT and misconfigured application override do not cause denial when a matching permit rule exists.
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 destination NAT is causing asymmetric routing.
Why it's wrong here
Destination NAT alters the translated destination address, but the stem describes a permit rule already matching source and destination, so NAT is not the cause. It is tempting because NAT causes asymmetric routing, and would be correct if return traffic bypassed the firewall.
- ✗
The rule is too far down in the rulebase and a previous implicit deny is blocking.
Why it's wrong here
PAN-OS evaluates rules top-down, so a matching permit above the deny would already have allowed the traffic; there is no implicit deny mid-rulebase. It is tempting because rule ordering matters, and would be correct if an explicit deny sat above the permit.
- ✓
A previous rule with a broader match is denying the traffic before reaching the permit rule.
Why this is correct
PAN-OS evaluates the rulebase top-down and stops at the first match. A broader deny rule positioned above the permit rule shadows it, so traffic from that subnet is dropped before the matching permit is ever evaluated.
- ✗
The application override is misconfigured.
Why it's wrong here
Application override changes App-ID classification for specific traffic; it does not deny traffic matching a permit rule's source and destination. It is tempting because App-ID mismatches cause unexpected blocks, and would be correct if the application were being identified as the wrong one.
Visual reference
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSA 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 PCNSA exam.