Quick Answer
The answer is operation mode, firmware version, and HA password (if set) must be identical on both FortiGate units for the cluster to form. This is because HA cluster formation requirements for FortiGate demand strict synchronization of core configuration parameters to ensure both devices operate as a single logical unit; mismatched operation mode (NAT or Transparent) or firmware versions would cause incompatible packet handling and state synchronization failures, while a mismatched HA password prevents secure heartbeat authentication. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this question tests your understanding of the HA formation prerequisites, often appearing as a trap where candidates mistakenly include priority or hostname—but priority is designed to differ to elect the primary unit, and hostname is merely a label. A reliable memory tip is to remember the three “must-match” pillars: Mode, Firmware, and Password—if any of these differ, the cluster will not form.
This NSE4 practice question tests your understanding of high availability and diagnostics. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator is configuring an active-passive HA pair. Which THREE of the following must be identical on both units for the cluster to form? (Choose three.)
HA priority
Why wrong: Should differ to elect active unit.
Hostname
Why wrong: Hostname can differ.
HA password
If configured, must match.
Firmware version
Must match.
Operation mode (NAT/Transparent)
Must match.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
HA password
Operation mode, firmware version, and HA password (if set) must match. Priority can differ. Hostname is not required to match.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
HA priority
Why it's wrong here
Should differ to elect active unit.
Hostname
Why it's wrong here
Hostname can differ.
HA password
Why this is correct
If configured, must match.
Related concept
Static NAT maps one inside address to one outside address.
Firmware version
Why this is correct
Must match.
Related concept
Static NAT maps one inside address to one outside address.
Operation mode (NAT/Transparent)
Why this is correct
Must match.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
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FAQ
High Availability and Diagnostics — This question tests High Availability and Diagnostics — Static NAT maps one inside address to one outside address..
The correct answer is: HA password — Operation mode, firmware version, and HA password (if set) must match. Priority can differ. Hostname is not required to match.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 2026
This NSE4 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 NSE4 exam.
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