- A
Disable anti-replay protection.
Why wrong: Disabling anti-replay would reduce security and may not significantly improve throughput.
- B
Enable hardware acceleration for VPN.
Hardware acceleration uses dedicated chips to handle crypto, freeing CPU and increasing throughput.
- C
Change the encryption algorithm to AES-128.
Why wrong: Weaker encryption may help, but hardware acceleration is a more direct solution and preserves security.
- D
Increase the MTU on the tunnel interface.
Why wrong: MTU changes may cause fragmentation; they don't address the underlying processing bottleneck.
Question 208 of 516
Why Your IPsec VPN Throughput Is Low: Enable Hardware Acceleration
This PCNSE practice question tests your understanding of troubleshoot. 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 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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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.
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.
- ✗
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.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates 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.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls use a dedicated crypto engine (e.g., on the PA-5200 series) that handles IPsec encryption/decryption in hardware, bypassing the dataplane CPU. When hardware acceleration is disabled or misconfigured, VPN traffic falls back to software-based crypto, which is slower even at 30% CPU utilization due to per-packet processing overhead. Enabling this feature via 'set network ipsec hardware-offload' or the GUI ensures that AES-256-GCM and SHA-256 operations are offloaded to the ASIC, achieving wire-speed throughput.
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.
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.
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FAQ
Questions learners often ask
What does this PCNSE question test?
Troubleshoot — This question tests Troubleshoot — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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