PCNSA Device Management and Services Practice Question
A network engineer wants to configure a new VLAN interface on a Palo Alto Networks firewall. After creating the VLAN object and assigning it to an Ethernet interface, the VLAN interface remains down. What is the most likely cause?
⚠ Common exam trap
Test-takers frequently assume a VLAN interface only needs an IP address or a virtual router assignment to come up, overlooking the prerequisite that the parent Ethernet interface must be in Layer 2 mode with the VLAN tag allowed.
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 Ethernet interface is not set to layer 2 mode or the VLAN tag is not allowed
For a VLAN interface to be operational on a Palo Alto Networks firewall, the underlying Ethernet interface must be configured in Layer 2 mode and the specific VLAN tag must be allowed on that interface. If the Ethernet interface remains in Layer 3 mode or the VLAN tag is not included in the allowed list, the VLAN interface will remain administratively down, as it cannot associate with a physical port that is not set to accept VLAN 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.
- ✗
The VLAN interface needs an IP address configured
Why it's wrong here
An IP address is needed for routing, but the interface can be up without one if the parent is configured correctly.
- ✗
The VLAN interface must be assigned to a virtual router
Why it's wrong here
A virtual router is needed for routing, but not for the interface to be administratively up.
- ✗
The firewall needs a commit to apply the changes
Why it's wrong here
Committing is needed, but the interface would still show down if the parent is misconfigured.
- ✓
The Ethernet interface is not set to layer 2 mode or the VLAN tag is not allowed
Why this is correct
For a VLAN interface to be up, the parent Ethernet interface must be in layer 2 mode and the VLAN tag must be in the allowed list.
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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.