PCNSA Device Management and Services Practice Question
A company has two Palo Alto Networks firewalls in active/passive HA. The passive firewall failed and was replaced with a new unit. The network administrator initiates a configuration sync from the active to the new passive. After the sync, the passive unit shows as 'Active' instead of 'Passive'. What is the most likely cause?
⚠ Common exam trap
Test-takers frequently assume a configuration sync will automatically update the peer serial number or that the HA role is determined solely by the 'device priority' setting, overlooking the explicit serial number validation required for HA peer authentication.
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
✓
The active firewall's HA settings were missing the new device's serial number.
In an active/passive HA pair, the active firewall maintains a list of allowed peer serial numbers. If the new passive unit's serial number is not included in the active firewall's HA configuration, the active will not recognize the passive as a valid peer. Consequently, the passive unit, lacking a proper HA heartbeat from the active, will assume the active role (become 'Active') due to a loss of the HA link or misidentification, as it defaults to active state when it cannot establish a proper HA relationship.
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 HA link is misconfigured on both units.
Why it's wrong here
HA link misconfiguration would prevent sync from completing.
- ✗
The passive unit's HA configuration was set to 'Stateful Inspection' instead of 'Passive'.
Why it's wrong here
'Stateful Inspection' is not an HA role configuration.
- ✓
The active firewall's HA settings were missing the new device's serial number.
Why this is correct
Missing serial number prevents authentication, causing passive to become active.
- ✗
The passive unit had a different version of Panorama template.
Why it's wrong here
Panorama templates do not affect HA role.
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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.