NSE7 Troubleshooting and Diagnostics Practice Question
A FortiGate in an HA cluster is experiencing intermittent session synchronization failures. The administrator runs 'diagnose sys ha dump sync-status' and sees that sessions are not being synchronized properly. Which TWO potential causes should the administrator investigate?
⚠ Common exam trap
Watch out — candidates often assume all HA synchronization failures are caused by network connectivity issues (high latency/packet loss) and overlook the session sync limit, which is a configuration-based threshold that can cause intermittent failures even with perfect heartbeat connectivity.
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
✓
Excessive number of sessions exceeding the session sync limit
FortiGate HA has a configurable session sync limit (default 500,000 sessions). When the number of concurrent sessions exceeds this limit, the FortiGate stops synchronizing new sessions to the backup unit, leading to intermittent synchronization failures. This can be verified by checking the 'ses_sync_limit' value in the HA configuration and comparing it to the current session count. Option D is correct because high packet loss or latency on the heartbeat interface can cause session synchronization failures. The heartbeat interface carries synchronization traffic, and any degradation in its performance can lead to missed or delayed sync packets, resulting in intermittent sync failures. This can be diagnosed by checking heartbeat interface statistics such as packet loss and latency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Mismatched HA group IDs
Why it's wrong here
Differing HA group IDs stop the devices recognising each other as cluster peers, so the cluster never establishes and no synchronisation occurs at all. Group ID matching is the right check when building a new cluster or when members show as standalone, not for intermittent sync faults.
- ✓
Excessive number of sessions exceeding the session sync limit
Why this is correct
FortiGate synchronises only a set number of sessions; once the session count exceeds that sync limit, additional sessions are not replicated to the secondary unit. This produces exactly the intermittent synchronisation failures observed, as only sessions beyond the threshold go unsynchronised.
- ✗
Incorrect BGP route advertisements
Why it's wrong here
BGP route advertisements affect Layer 3 reachability and path selection, not the HA session-sync channel, which uses the dedicated HA heartbeat and sync interfaces. Verifying BGP is correct when failover succeeds but traffic takes a suboptimal path afterwards.
- ✓
High packet loss or latency on the heartbeat interface
Why this is correct
HA session synchronisation traverses the heartbeat interface, so packet loss or latency there delays or drops sync packets between cluster members. This directly explains intermittent failures, since the heartbeat link must reliably carry session state for the cluster to stay synchronised.
- ✗
Mismatched HA passwords
Why it's wrong here
Mismatched HA passwords prevent the cluster from forming or cause members to leave the group entirely, which surfaces as HA status errors rather than selective session-sync failures. Password alignment is the correct check when a FortiGate cannot join an HA cluster at all.
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JA
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.