The answer is SSL decryption enabled and processing many sessions. This is the most likely cause of high dataplane CPU because SSL decryption forces the firewall to perform resource-intensive asymmetric and symmetric cryptographic operations for every session, including terminating and re-encrypting TLS connections. Even with only 45,000 active sessions out of a 100,000 maximum, the per-session overhead of decryption can spike CPU usage to 85%, far more than other factors like session count alone. On the Palo Alto Networks Certified Network Security Engineer PCNSE exam, this question tests your understanding that dataplane CPU spikes are often tied to compute-heavy features, not just session limits—a common trap is assuming high CPU always means too many sessions. Remember the mnemonic: “SSL eats CPU for breakfast,” meaning decryption overhead, not session volume, is the usual culprit.
PCNSE Manage, Monitor and Operate Practice Question
This PCNSE practice question tests your understanding of manage, monitor and operate. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Exhibit
Refer to the exhibit.
admin@PA-3020> show session info
Total active sessions: 45000
TCP sessions: 40000
UDP sessions: 5000
admin@PA-3020> show session stats
Max sessions: 100000
Current sessions: 45000
admin@PA-3020> show running resource-monitor
Dataplane CPU: 85%
Refer to the exhibit. The firewall is experiencing high dataplane CPU usage (85%) with 45,000 active sessions out of a maximum of 100,000. Which of the following is the most likely cause of the high CPU?
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.
Refer to the exhibit.
admin@PA-3020> show session info
Total active sessions: 45000
TCP sessions: 40000
UDP sessions: 5000
admin@PA-3020> show session stats
Max sessions: 100000
Current sessions: 45000
admin@PA-3020> show running resource-monitor
Dataplane CPU: 85%
A
SSL decryption is enabled and processing many sessions
SSL decryption is CPU-intensive.
B
The firewall is reaching its maximum session limit
Why wrong: Session count is only 45% of max.
C
The firewall is under a DDoS attack
Why wrong: DDoS would likely cause session count to be much higher.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SSL decryption is enabled and processing many sessions
SSL decryption is a highly CPU-intensive operation because it requires the firewall to terminate and re-encrypt TLS connections, performing asymmetric and symmetric cryptographic operations for each session. With 45,000 active sessions, even if the session count is below the 100,000 limit, the per-session processing overhead of SSL decryption can drive dataplane CPU to 85%.
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.
✓
SSL decryption is enabled and processing many sessions
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume high CPU must be due to reaching session limits or an attack, but Cisco tests the understanding that SSL decryption's per-session cryptographic overhead can cause high CPU even at moderate session counts.
Detailed technical explanation
How to think about this question
SSL decryption on Palo Alto firewalls uses the dataplane CPU to perform RSA key exchange, AES encryption/decryption, and certificate validation per session. The firewall can offload some crypto to hardware acceleration (e.g., on PA-5200 series), but on many models, especially virtual or lower-end appliances, the dataplane CPU handles all TLS termination, making it a common bottleneck. In real-world scenarios, enabling SSL decryption on a firewall with moderate session counts can spike CPU to 80-90% even when other resources (memory, session table) are well within limits.
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.
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.
Manage, Monitor and Operate — This question tests Manage, Monitor and Operate — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SSL decryption is enabled and processing many sessions — SSL decryption is a highly CPU-intensive operation because it requires the firewall to terminate and re-encrypt TLS connections, performing asymmetric and symmetric cryptographic operations for each session. With 45,000 active sessions, even if the session count is below the 100,000 limit, the per-session processing overhead of SSL decryption can drive dataplane CPU to 85%.
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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Question Discussion
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