PCNSE Troubleshoot Practice Question
A firewall is experiencing high CPU utilization. The engineer suspects a denial-of-service attack. Which command should be used to identify the source of the attack?
⚠ Common exam trap
Candidates often choose 'debug flow basic' (option D) because they think deep packet inspection is needed to find the attack source, but this command is too resource-intensive and does not directly identify the source IP; instead, the session table query is the correct first step.
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
✓
show session all | match <source IP>
The 'show session all' command displays all active sessions on the firewall, and piping the output to 'match <source IP>' filters for sessions originating from a specific IP address. In a high CPU scenario suspected to be a DoS attack, this allows the engineer to quickly identify if a single source IP is generating an excessive number of sessions, which is a common indicator of a flood-based attack.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
show counter global | match drop
Why it's wrong here
This shows drop counters but doesn't identify the source of an attack.
- ✓
show session all | match <source IP>
Why this is correct
This command lists all sessions and can be filtered to see if a single source has many sessions.
- ✗
request high-availability state
Why it's wrong here
This command is for HA state, not troubleshooting CPU utilization.
- ✗
debug flow basic
Why it's wrong here
Debug flow basic is used for packet flow debugging, not for identifying high session counts.
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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.