- A
Create a decryption policy to decrypt all traffic.
Why wrong: Decryption does not interact with authentication enforcement.
- B
Use identity-based routing to enforce authentication.
Why wrong: Identity-based routing is for policy-based routing, not authentication.
- C
Enable user-ID on the ingress interface and configure authentication policy for IP addresses.
Why wrong: This is already assumed; the issue is that the existing authentication policy may not match the IP address range. More specific is needed.
- D
Configure an authentication policy with source user 'unknown' to enforce authentication for all unmapped IP addresses.
By default, authentication policies match on source user 'any', so if a user mapping exists, the policy applies. Setting source user to 'unknown' ensures that traffic from IPs without a user mapping triggers authentication.
How to Prevent Authentication Bypass When Users Access Resources by IP Address
This PCNSE practice question tests your understanding of securing users and applications with authentication. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 security administrator notices that users are able to bypass authentication by accessing resources using IP addresses instead of FQDNs, even though authentication policies are configured. How can this be prevented?
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
Configure an authentication policy with source user 'unknown' to enforce authentication for all unmapped IP addresses.
Option D is correct because when users access resources by IP address rather than FQDN, the firewall cannot associate the traffic with a specific user via normal authentication policies (which rely on domain-based rules). By configuring an authentication policy with source user 'unknown', the firewall forces authentication for all unmapped IP addresses, ensuring that even IP-based access triggers user identification and policy enforcement.
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.
- ✗
Create a decryption policy to decrypt all traffic.
Why it's wrong here
Decryption does not interact with authentication enforcement.
- ✗
Use identity-based routing to enforce authentication.
Why it's wrong here
Identity-based routing is for policy-based routing, not authentication.
- ✗
Enable user-ID on the ingress interface and configure authentication policy for IP addresses.
Why it's wrong here
This is already assumed; the issue is that the existing authentication policy may not match the IP address range. More specific is needed.
- ✓
Configure an authentication policy with source user 'unknown' to enforce authentication for all unmapped IP addresses.
Why this is correct
By default, authentication policies match on source user 'any', so if a user mapping exists, the policy applies. Setting source user to 'unknown' ensures that traffic from IPs without a user mapping triggers authentication.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume enabling User-ID on the interface or using decryption will solve the bypass, but they miss the critical detail that authentication policies must explicitly target unmapped IPs via the 'unknown' source user to enforce authentication for IP-based access.
Detailed technical explanation
How to think about this question
Under the hood, Palo Alto Networks firewalls maintain a User-ID mapping table that correlates IP addresses to usernames. When a user accesses a resource via FQDN, the firewall can intercept the HTTP request and prompt for authentication; however, direct IP access bypasses this interception. The 'unknown' user setting in the authentication policy forces the firewall to challenge any traffic from an unmapped IP, regardless of whether the destination is an FQDN or IP address, effectively closing the bypass vector.
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 practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
- →
Securing Users and Applications with Authentication — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Securing Users and Applications with Authentication — This question tests Securing Users and Applications with Authentication — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure an authentication policy with source user 'unknown' to enforce authentication for all unmapped IP addresses. — Option D is correct because when users access resources by IP address rather than FQDN, the firewall cannot associate the traffic with a specific user via normal authentication policies (which rely on domain-based rules). By configuring an authentication policy with source user 'unknown', the firewall forces authentication for all unmapped IP addresses, ensuring that even IP-based access triggers user identification and policy enforcement.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on PCNSE
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security admin receives reports that some users are bypassing authentication by manually setting a different IP address. Which feature can enforce that only users who have authenticated through the firewall can access resources?
easy- ✓ A.Authentication Policy requiring authentication for all traffic
- B.GlobalProtect client certificate authentication
- C.Security policy using source-user attribute
- D.Captive Portal with cookie-based authentication
Why A: Option A is correct because Authentication Policy enforces authentication for all traffic, ensuring that only authenticated users can access resources regardless of their IP address. This prevents bypassing by manually setting a different IP. Option B (GlobalProtect client certificate authentication) does not prevent IP spoofing as certificates are tied to devices, not IPs. Option C (Security policy using source-user attribute) relies on User-ID mapping, which can be spoofed if the IP is changed before mapping. Option D (Captive Portal with cookie-based authentication) can be bypassed if the user does not go through the portal or if cookies are manipulated.
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Last reviewed: Jul 4, 2026
This PCNSE 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 PCNSE exam.
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