PCNSE Deploy and Configure Firewalls Practice Question
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
Refer to the exhibit.
admin@PA-500# show running config | match nat
...
nat {
source-nat {
rule "SNAT-Outside" {
source [ 10.0.0.0/8 ];
destination [ any ];
service [ any ];
to-interface ethernet1/1;
source-translation {
interface-address;
}
}
}
}
The source NAT rule 'SNAT-Outside' is configured to translate traffic from 10.0.0.0/8 to the interface address of ethernet1/1. However, traffic from 10.1.1.1 to the internet is not being translated. What is the most likely reason?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The rule is missing a 'from' zone specification.
Option B is correct because a source NAT rule in PAN-OS requires a 'from' zone specification to match traffic. Without it, the rule does not know which zone the traffic originates from, so it will not be applied. In this case, the traffic from 10.1.1.1 to the internet likely originates from a zone (e.g., 'trust') that is not specified in the rule, causing the translation to fail.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 'interface-address' option requires a specific translated address.
Why it's wrong here
Interface-address uses the IP of the specified interface dynamically.
✓
The rule is missing a 'from' zone specification.
Why this is correct
Source NAT rules must include the source zone to determine when to translate.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The rule should be under 'destination-nat' instead of 'source-nat'.
Why it's wrong here
This is a source NAT scenario; destination NAT is for inbound traffic.
✗
The 'to-interface' should be 'any'.
Why it's wrong here
Specifying the egress interface is correct and often necessary.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume source NAT rules only need a source IP range and an egress interface, overlooking the mandatory 'from' zone specification that PAN-OS requires for rule matching.
Trap categories for this question
Scenario analysis trap
This is a source NAT scenario; destination NAT is for inbound traffic.
Detailed technical explanation
How to think about this question
In PAN-OS, source NAT rules are evaluated based on zone matching (from/to zones) and security policy. The 'from' zone is mandatory for the rule to be triggered; if omitted, the rule is effectively disabled. Under the hood, the firewall's dataplane uses the zone information to determine which NAT rule to apply, and without it, the packet bypasses the rule entirely. A real-world scenario is when an administrator configures NAT rules but forgets to specify the source zone (e.g., 'trust'), causing traffic from that zone to remain untranslated.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deploy and Configure Firewalls — This question tests Deploy and Configure Firewalls — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The rule is missing a 'from' zone specification. — Option B is correct because a source NAT rule in PAN-OS requires a 'from' zone specification to match traffic. Without it, the rule does not know which zone the traffic originates from, so it will not be applied. In this case, the traffic from 10.1.1.1 to the internet likely originates from a zone (e.g., 'trust') that is not specified in the rule, causing the translation to fail.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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