- A
The encryption algorithm must be set to null.
Why wrong: Incorrect. Setting null encryption would disable encryption, not cause no encryption.
- B
A NAT policy to translate private addresses.
Why wrong: Incorrect. NAT is not required for VPN; encryption can happen on private IPs.
- C
A security policy allowing traffic from the tunnel interface to the destination.
Correct. Without a policy, traffic is dropped.
- D
The tunnel interface must be assigned to a security zone.
Why wrong: Incorrect. Tunnel interfaces can be in the default zone; missing zone does not prevent encryption.
Question 510 of 516
IPSec Tunnel Active but No Encryption: Missing Security Policy
This PCNSE practice question tests your understanding of secure access and vpn. 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.
An administrator configures a VPN tunnel between two Palo Alto firewalls. The tunnel shows as active, but traffic is not being encrypted. What configuration step is most likely missing?
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 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 security policy allowing traffic from the tunnel interface to the destination.
Option C is correct because even when a VPN tunnel is active (Phase 1 and Phase 2 SAs are established), traffic will not be encrypted unless a security policy explicitly permits traffic from the tunnel interface to the destination zone. On Palo Alto firewalls, inter-zone traffic requires a security policy to allow the session; without it, the firewall drops the traffic before it can be encrypted and sent over the tunnel. The tunnel being up only indicates IKE/IPsec negotiation succeeded, not that data-plane forwarding is authorized.
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 encryption algorithm must be set to null.
Why it's wrong here
Incorrect. Setting null encryption would disable encryption, not cause no encryption.
- ✗
A NAT policy to translate private addresses.
- ✓
A security policy allowing traffic from the tunnel interface to the destination.
Why this is correct
Correct. Without a policy, traffic is dropped.
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 tunnel interface must be assigned to a security zone.
Why it's wrong here
Incorrect. Tunnel interfaces can be in the default zone; missing zone does not prevent encryption.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume an active VPN tunnel automatically encrypts all traffic routed to it, overlooking that Palo Alto firewalls enforce security policies as a prerequisite for any inter-zone traffic, including traffic destined for a tunnel interface.
Detailed technical explanation
How to think about this question
Under the hood, Palo Alto firewalls use a virtual tunnel interface (tunX) that must be placed in a security zone (e.g., 'VPN') and referenced in a security policy rule that allows traffic from the source zone (e.g., 'Trust') to the tunnel zone. Even with correct IPsec configuration, the firewall's session table will not create a session for the encrypted flow unless a security policy match occurs; the traffic is dropped at the ingress zone lookup. In real-world scenarios, administrators often verify tunnel status via 'show vpn ike-sa' and 'show vpn ipsec-sa' but forget that inter-zone traffic requires an explicit allow rule, leading to a 'tunnel up, no traffic' symptom.
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.
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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.
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Secure Access and VPN — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Secure Access and VPN — This question tests Secure Access and VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A security policy allowing traffic from the tunnel interface to the destination. — Option C is correct because even when a VPN tunnel is active (Phase 1 and Phase 2 SAs are established), traffic will not be encrypted unless a security policy explicitly permits traffic from the tunnel interface to the destination zone. On Palo Alto firewalls, inter-zone traffic requires a security policy to allow the session; without it, the firewall drops the traffic before it can be encrypted and sent over the tunnel. The tunnel being up only indicates IKE/IPsec negotiation succeeded, not that data-plane forwarding is authorized.
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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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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