The answer is unoptimized security policy rules, which force excessive traffic through App-ID processing. When security policies lack proper application-based entries or are too broad, the firewall must perform deep packet inspection on every session to identify the application, creating a backlog of pending App-ID sessions. This overwhelms the dataplane CPU because each session waits for identification before a security decision can be made, directly causing high CPU utilization with many pending App-ID sessions. On the PCNSE exam, this scenario tests your understanding of how policy order and specificity impact performance—a common trap is to blame hardware limitations or attack traffic instead of recognizing that poorly structured rules force unnecessary inspection. Remember the memory tip: “Broad policies breed backlogs.” Optimize by moving application-specific rules above generic allow rules and using application defaults to reduce the inspection load.
PCNSE Securing Traffic and App-ID Practice Question
This PCNSE practice question tests your understanding of securing traffic and app-id. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 state | match appid
total appid sessions: 12000
appid pending sessions: 4500
appid complete sessions: 7500
appid error sessions: 0
Refer to the exhibit. A network engineer notices high CPU utilization on the firewall. The output shows that 4500 sessions are pending App-ID identification. What is the most likely cause of the high number of pending sessions?
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.
show system state | match appid
total appid sessions: 12000
appid pending sessions: 4500
appid complete sessions: 7500
appid error sessions: 0
A
An application override policy is being used extensively.
Why wrong: Application override bypasses App-ID, so it would not increase pending sessions.
B
Security policy rules are not optimized, causing excessive traffic to be processed by App-ID.
Poorly designed security policies can cause unnecessary traffic to be inspected, leading to a high number of pending sessions.
C
SSL decryption is disabled for most traffic.
Why wrong: Disabling decryption reduces the amount of traffic that App-ID needs to inspect, decreasing pending sessions.
D
The application database is outdated and missing signatures.
Why wrong: Missing signatures would likely cause error sessions, not pending sessions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Security policy rules are not optimized, causing excessive traffic to be processed by App-ID.
When security policy rules are not optimized, excessive traffic may be processed by App-ID, causing a backlog of sessions waiting for application identification. The firewall's dataplane can become overwhelmed if too many sessions require deep packet inspection before a decision is made, leading to high CPU utilization and a large number of pending App-ID sessions.
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.
✗
An application override policy is being used extensively.
Why it's wrong here
Application override bypasses App-ID, so it would not increase pending sessions.
✓
Security policy rules are not optimized, causing excessive traffic to be processed by App-ID.
Why this is correct
Poorly designed security policies can cause unnecessary traffic to be inspected, leading to a high number of pending sessions.
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.
✗
SSL decryption is disabled for most traffic.
Why it's wrong here
Disabling decryption reduces the amount of traffic that App-ID needs to inspect, decreasing pending sessions.
✗
The application database is outdated and missing signatures.
Why it's wrong here
Missing signatures would likely cause error sessions, not pending sessions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a high number of pending App-ID sessions is caused by a lack of signatures or decryption, when in fact it is typically a symptom of rulebase inefficiency that forces excessive traffic through the App-ID engine.
Detailed technical explanation
How to think about this question
App-ID uses multiple identification mechanisms in parallel, including protocol decoding, application signatures, and behavioral analysis. When security rules are not optimized, the firewall may attempt to apply App-ID to traffic that could have been allowed or denied earlier in the rulebase, increasing the number of sessions that require full inspection. In high-throughput environments, this can exhaust the session setup rate, causing sessions to queue in a pending state while waiting for App-ID to complete.
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.
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Security policy rules are not optimized, causing excessive traffic to be processed by App-ID. — When security policy rules are not optimized, excessive traffic may be processed by App-ID, causing a backlog of sessions waiting for application identification. The firewall's dataplane can become overwhelmed if too many sessions require deep packet inspection before a decision is made, leading to high CPU utilization and a large number of pending App-ID sessions.
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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