The answer is that the firewall has reached its session limit. This is correct because when a Palo Alto Networks firewall exhausts its maximum concurrent session capacity—a hard resource ceiling determined by the specific platform model and any session-based licensing—it will drop new connection attempts to protect existing traffic already established in the session table. The firewall’s design prioritizes keeping active sessions alive, so they continue to flow normally until they age out or are terminated, while any new SYN packets are silently discarded. On the PCNSA exam, this scenario tests your understanding of session limit exhaustion as a distinct failure mode, often appearing in exhibits showing a sudden spike in denied connections alongside stable throughput. A common trap is confusing this with performance degradation or DoS attacks, but the key clue is that only new sessions fail. Memory tip: think of a full parking lot—existing cars stay, but no new cars can enter until a space opens.
PCNSA Palo Alto Networks Platforms and Architecture Practice Question
This PCNSA practice question tests your understanding of palo alto networks platforms and architecture. 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.
> show system info
Hardware model: PA-5250
Serial number: 007200000123
Software version: 10.1.3
System uptime: 14 days, 3 hours, 22 minutes
System time: Tue Jul 25 14:35:12 2023
Eth0/0: 192.168.1.1/24
Eth0/1: 10.0.0.1/24
Sessions active: 25000
Devices active: 120
Based on the exhibit, what is the most likely cause if the firewall is dropping new connections but existing sessions continue to work?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The firewall has reached its session limit.
When a Palo Alto Networks firewall reaches its maximum session capacity (defined by the platform model and license), it will drop new connection attempts while maintaining existing sessions that are already in the session table. This behavior is by design to preserve established traffic. The session limit is a hard resource constraint, not a performance degradation, so existing flows continue uninterrupted until they age out or are terminated.
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.
✓
The firewall has reached its session limit.
Why this is correct
25k sessions may be near the limit for PA-5250, causing denial of new connections.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The management interface IP (192.168.1.1) is conflicting with another device.
Why it's wrong here
Does not affect session creation.
✗
The firewall is low on CPU memory.
Why it's wrong here
Not shown in exhibit and session limit is more likely.
✗
The software version 10.1.3 is buggy.
Why it's wrong here
No indication of a bug; version is recent.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse session limit exhaustion with general resource starvation (like CPU or memory), but the key differentiator is that only new connections are affected while existing sessions remain fully functional, which is a hallmark of hitting the session table cap.
Trap categories for this question
Command / output trap
Not shown in exhibit and session limit is more likely.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls use a session table stored in high-speed memory (e.g., DRAM or TCAM depending on model) with a fixed maximum number of concurrent sessions. When the session table is full, the firewall's session setup process (which involves a three-way handshake for TCP or first-packet processing for UDP) is denied, but the existing session entries remain active until they time out (e.g., TCP timeout defaults to 3600 seconds for established sessions). This can be verified via 'show session info' or 'show running resource-monitor' CLI commands, which display current session counts and 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.
Palo Alto Networks Platforms and Architecture — This question tests Palo Alto Networks Platforms and Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall has reached its session limit. — When a Palo Alto Networks firewall reaches its maximum session capacity (defined by the platform model and license), it will drop new connection attempts while maintaining existing sessions that are already in the session table. This behavior is by design to preserve established traffic. The session limit is a hard resource constraint, not a performance degradation, so existing flows continue uninterrupted until they age out or are terminated.
What should I do if I get this PCNSA 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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