NSE7 Troubleshooting and Diagnostics Practice Question
A FortiGate in an HA cluster shows the message 'split-brain detected' in the event log. The administrator checks the HA status and sees both units are in 'standalone' mode. What is the MOST likely cause of this split-brain scenario?
⚠ Common exam trap
It's easy for candidates to assume split-brain is caused by configuration mismatches (like priority or mode), but the core issue is always a loss of heartbeat communication between the cluster members, leading both to operate independently in standalone mode.
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 heartbeat interface is down on both units, causing them to assume they are the primary
When the heartbeat interface fails on both units, each FortiGate loses communication with its peer and assumes it is the sole surviving unit. This causes both to transition to 'standalone' mode and operate independently, which is the classic split-brain scenario. The event log message 'split-brain detected' confirms that the cluster has lost heartbeat connectivity, leading to each unit believing it must take over as primary.
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 heartbeat interface is down on both units, causing them to assume they are the primary
Why this is correct
When heartbeat communication is lost, both units may assume primary role, leading to split-brain.
- ✗
The HA priority is set to the same value on both units
Why it's wrong here
Same priority can cause election issues but not typically split-brain; one will still become primary.
- ✗
The HA mode is set to 'active-active' instead of 'active-passive'
Why it's wrong here
Active-active mode does not cause split-brain; both units are active but with session load balancing.
- ✗
The HA cluster is using a unicast heartbeat and the configuration is incorrect
Why it's wrong here
Incorrect unicast configuration can prevent heartbeat, leading to split-brain, but the primary cause is loss of heartbeat.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE7 practice question is part of Courseiva's free Fortinet 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 NSE7 exam.