PCNSE Troubleshoot Practice Question
A network engineer is troubleshooting a slow file transfer through a PA-5200. The file transfer is between two sites connected via IPsec VPN. The firewall has a symmetric crypto profile with AES-256 and SHA-256. The throughput is lower than expected. The engineer checks the dataplane CPU and sees it is 30%. The firewall's interface counters show no errors. What should be the first step to improve throughput?
⚠ Common exam trap
Test-takers frequently assume low CPU means no bottleneck, but in VPN scenarios, software-based crypto can be the limiting factor even with low CPU because the dataplane CPU is not the only resource involved; hardware acceleration must be explicitly enabled.
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
✓
Enable hardware acceleration for VPN.
The PA-5200 firewall has dedicated hardware acceleration for IPsec VPN processing, which offloads crypto operations from the dataplane CPU. With the dataplane CPU at only 30% and no interface errors, the bottleneck is likely that the VPN traffic is being processed in software rather than hardware. Enabling hardware acceleration (option B) allows the firewall to use its onboard crypto engine, significantly improving throughput for AES-256 and SHA-256 operations.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable anti-replay protection.
Why it's wrong here
Disabling anti-replay would reduce security and may not significantly improve throughput.
- ✓
Enable hardware acceleration for VPN.
Why this is correct
Hardware acceleration uses dedicated chips to handle crypto, freeing CPU and increasing throughput.
- ✗
Change the encryption algorithm to AES-128.
Why it's wrong here
Weaker encryption may help, but hardware acceleration is a more direct solution and preserves security.
- ✗
Increase the MTU on the tunnel interface.
Why it's wrong here
MTU changes may cause fragmentation; they don't address the underlying processing bottleneck.
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.