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PCNSA Practice Question: An administrator is configuring Network Address…
An administrator is configuring Network Address Translation (NAT) on a Palo Alto Networks firewall. Which of the following statements about the order of NAT rule evaluation is correct?
⚠ Common exam trap
The trap here is that candidates familiar with Cisco ASA or router NAT (which often uses order-independent or longest-match logic) assume the same applies to Palo Alto, but Palo Alto strictly uses top-down first-match evaluation for NAT rules, and NAT is processed before security rules.
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
✓
NAT rules are evaluated from top to bottom, and the first match is applied
Palo Alto Networks firewalls evaluate NAT rules from top to bottom in the rulebase, applying the first matching rule to the traffic. This is analogous to security rule evaluation order, ensuring deterministic behavior for source and destination translation. Once a NAT rule matches, no further NAT rules are considered for that session.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NAT rules are evaluated after security rules
Why it's wrong here
NAT rules are evaluated before security rules, so this reverses the actual order. It is tempting because security policy is the firewall's headline function, and NAT is often configured alongside it, but the firewall translates the packet first, then matches the translated addresses against security policy.
- ✓
NAT rules are evaluated from top to bottom, and the first match is applied
Why this is correct
Palo Alto Networks evaluates NAT rules sequentially from the top of the rulebase downwards, applying the first rule whose match criteria are satisfied. This top-to-bottom, first-match order means rule placement directly determines which translation is applied, so more specific rules must sit above broader ones.
- ✗
NAT rules use longest prefix match on the destination address
Why it's wrong here
Palo Alto Networks evaluates NAT rules top-down in rulebase order, not by longest prefix match; that mechanism belongs to routing table lookups. It tempts because prefix matching governs route selection, and would be correct when describing how the firewall chooses among competing routes.
- ✗
NAT rules cannot combine source and destination NAT in a single rule
Why it's wrong here
A single NAT rule can perform source and destination translation together, so this statement is false. It tempts because many platforms separate source and destination NAT policies, and would be correct when describing those platforms rather than Palo Alto Networks.
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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.