PCNSE Troubleshoot Practice Question
Which THREE components should be verified when troubleshooting a site-to-site IPSec VPN that is not coming up?
⚠ Common exam trap
Watch out — candidates often confuse zone protection profiles or interface management profiles with VPN-related security settings, but these profiles only affect data-plane or management-plane traffic, not the control-plane IKE negotiation required for tunnel establishment.
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
✓
Pre-shared key configuration on both ends
The pre-shared key (PSK) must match exactly on both VPN peers. If the PSK differs, IKE Phase 1 authentication fails, preventing the tunnel from establishing. This is a fundamental requirement for both IKEv1 and IKEv2, as the PSK is used to generate authentication keys during the main or aggressive mode exchange.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Zone protection profile on the untrust zone
Why it's wrong here
Zone protection profiles mitigate floods, not VPN issues.
- ✗
Interface management profile on the external interface
Why it's wrong here
Management profiles control access to the firewall itself, not VPN.
- ✓
Pre-shared key configuration on both ends
Why this is correct
Mismatched PSK will prevent IKE authentication.
- ✓
Peer IP address in the tunnel interface configuration
Why this is correct
Incorrect peer IP will prevent the tunnel from establishing.
- ✓
IKE version (v1 vs v2) compatibility
Why this is correct
If one end uses IKEv1 and the other IKEv2, the tunnel fails.
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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.