- A
Create a security rule with an address group containing the 500 IPs as destination, action deny, placed above the allow rule.
Why wrong: Incorrect. Address groups are better than individual objects, but still require manual updates. An EDL is more efficient for dynamic lists.
- B
Create a security rule with source zone Trust, destination zone Untrust, source address list containing the 500 IPs, action deny.
Why wrong: Incorrect. The source address should be Trust zone, but the malicious IPs are destinations, not sources.
- C
Create an External Dynamic List (EDL) of the malicious IPs and reference it in a security rule as destination address, with action deny, placed above the allow rule.
Correct. EDLs simplify management and allow automatic updates, making them the most efficient choice for frequently changing lists.
- D
Create a security rule with source zone Trust, destination zone Untrust, destination address list containing the 500 IPs as separate address objects, action deny, placed above the allow rule.
Why wrong: Incorrect. Adding 500 individual objects is inefficient and hard to maintain.
Quick Answer
The answer is to create an External Dynamic List (EDL) of the malicious IPs and reference it in a security rule as the destination address with action deny, placed above the allow rule. This is the most efficient approach because EDLs are specifically designed to manage large, frequently changing IP lists—like the 500 malicious addresses here—by automatically updating the firewall without requiring manual reconfiguration. On the Palo Alto Networks Certified Network Security Administrator PCNSA exam, this question tests your understanding of how to scale security policies for dynamic threats, often contrasting EDLs against static address objects or manual entries, which would be impractical for frequent changes. A common trap is to suggest using a single static address group, but that fails when IPs change; the key insight is that EDLs offload list management to an external source. Remember the memory tip: “EDL for dynamic hell”—when IPs change fast, let the external list handle the task.
PCNSA Policy Evaluation and Management Practice Question
This PCNSA practice question tests your understanding of policy evaluation and management. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
A small business has a Palo Alto Networks firewall with a single security policy rule that allows all traffic from the 'Trust' zone to the 'Untrust' zone. The business recently experienced a malware infection originating from an internal host that communicated with known malicious IP addresses. The administrator wants to implement a security policy to block traffic to these malicious IP destinations. The administrator has a list of 500 malicious IP addresses that may change frequently. What is the most efficient way to create a policy to block traffic to these IPs?
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
Create an External Dynamic List (EDL) of the malicious IPs and reference it in a security rule as destination address, with action deny, placed above the allow rule.
External Dynamic Lists (EDLs) are designed to manage large, frequently updated lists of IP addresses. They integrate with security rules and can be updated automatically, minimizing administrative overhead.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a security rule with an address group containing the 500 IPs as destination, action deny, placed above the allow rule.
Why it's wrong here
Incorrect. Address groups are better than individual objects, but still require manual updates. An EDL is more efficient for dynamic lists.
- ✗
Create a security rule with source zone Trust, destination zone Untrust, source address list containing the 500 IPs, action deny.
Why it's wrong here
Incorrect. The source address should be Trust zone, but the malicious IPs are destinations, not sources.
- ✓
Create an External Dynamic List (EDL) of the malicious IPs and reference it in a security rule as destination address, with action deny, placed above the allow rule.
Why this is correct
Correct. EDLs simplify management and allow automatic updates, making them the most efficient choice for frequently changing lists.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Create a security rule with source zone Trust, destination zone Untrust, destination address list containing the 500 IPs as separate address objects, action deny, placed above the allow rule.
Why it's wrong here
Incorrect. Adding 500 individual objects is inefficient and hard to maintain.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSA NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this PCNSA question test?
Policy Evaluation and Management — This question tests Policy Evaluation and Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create an External Dynamic List (EDL) of the malicious IPs and reference it in a security rule as destination address, with action deny, placed above the allow rule. — External Dynamic Lists (EDLs) are designed to manage large, frequently updated lists of IP addresses. They integrate with security rules and can be updated automatically, minimizing administrative overhead.
What should I do if I get this PCNSA question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSA NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
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.
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