hardMultiple ChoiceObjective-mapped
PCNSA Practice Question: Your organization has deployed a Palo Alto…
Your organization has deployed a Palo Alto Networks PA-5250 firewall in a high-availability active/passive configuration. The firewall is connected to two ISPs for redundancy. The internal network uses OSPF with the firewall as an ASBR redistributing a default route. Recently, users reported intermittent connectivity to external resources. During troubleshooting, you notice that the active firewall's management interface has high CPU usage, and the show session all command displays many sessions in the 'active' state but with minimal data transfer. The passive firewall shows no such issues. The OSPF neighbor relationships are stable. What is the most likely cause of the intermittent connectivity?
⚠ Common exam trap
The trap here is that candidates often attribute high CPU on the management interface to a DDoS attack or license issues, but the key clue is the 'active' sessions with minimal data transfer, which points to asymmetric routing in an HA environment rather than a control-plane attack or feature degradation.
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
✓
Asymmetric routing is occurring due to a misconfiguration in the active/passive HA setup.
In an active/passive HA configuration, only the active firewall processes traffic. If asymmetric routing occurs—where traffic from the internal network to the internet uses one ISP link on the active firewall, but return traffic arrives via the other ISP link—the active firewall may see the return traffic as a new session or a non-symmetric flow. This causes the firewall to create sessions that remain in 'active' state with minimal data transfer, as the firewall attempts to match return packets to existing sessions but fails due to path asymmetry. The high CPU on the management interface results from the control plane processing these mismatched sessions, while the passive firewall is unaffected because it does not handle traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
OSPF is flapping and causing route instability.
Why it's wrong here
OSPF neighbors are stable, so flapping is not present.
- ✓
Asymmetric routing is occurring due to a misconfiguration in the active/passive HA setup.
Why this is correct
Asymmetric routing can cause sessions to be stuck and high management CPU as the firewall tries to process out-of-state packets.
- ✗
A DDoS attack is overwhelming the management plane.
Why it's wrong here
DDoS would affect dataplane more, and management CPU would not be sole symptom.
- ✗
The firewall's licenses have expired, causing feature degradation.
Why it's wrong here
License expiry would not cause the described symptoms.
Visual reference
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
Go deeper
Related to this question
About these practice questions
One of 516 original PCNSA practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSA 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 PCNSA exam.