NSE4 System and Network Administration Practice Question
Which protocol does FortiGate use to synchronize sessions between HA cluster members?
⚠ Common exam trap
The trap here is that candidates familiar with Cisco or open-standard redundancy protocols (HSRP, VRRP) may assume FortiGate uses one of those, but FortiGate relies on its proprietary FGCP for HA session synchronization.
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
✓
FGCP
FortiGate uses the FortiGate Cluster Protocol (FGCP) to synchronize session tables, configuration, and state information between HA cluster members. FGCP is a proprietary protocol that ensures seamless failover by replicating session data in real time, allowing the backup unit to take over active sessions without interruption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HSRP
Why it's wrong here
HSRP is a Cisco-proprietary First Hop Redundancy Protocol (FHRP) that provides default-gateway failover for end hosts. FortiGate firewalls do not use HSRP for high availability, and it does not carry session state or synchronize firewall sessions. Since HSRP operates only at Layer 3 with a virtual IP/MAC, it cannot preserve established TCP/UDP flows during a device failure, which is exactly why FortiGate relies on its own protocol instead.
- ✗
OSPF
Why it's wrong here
OSPF (Open Shortest Path First) is a link-state interior gateway routing protocol used to exchange layer-3 route information between routers. It has no mechanism for replicating session state, NAT translations, or firewall connection tables, and its purpose is to compute optimal paths rather than provide high-availability state synchronization. FortiGate uses OSPF for dynamic routing alongside its HA capability, but it is never involved in synchronizing sessions between cluster units.
- ✗
VRRP
Why it's wrong here
VRRP is an open-standard First Hop Redundancy Protocol that allows multiple routers to share a virtual IP for gateway redundancy, but it is inherently stateless. Some firewall vendors use VRRP for device failover, but FortiGate HA relies on the proprietary FGCP instead, which performs deep session and configuration synchronization. Even where VRRP is deployed, it only changes which physical device owns the virtual IP; it does not copy session tables, so existing connections would be dropped on failover.
- ✓
FGCP
Why this is correct
FGCP (FortiGate Clustering Protocol) is FortiGate's proprietary protocol designed to synchronize firewall sessions, configuration, and state information across HA cluster members. It continuously replicates session tables, including NAT mappings, TCP state, and UDP flows, over a dedicated heartbeat or HA link, enabling transparent failover with no session interruption. FGCP supports both active-passive and active-active HA modes and is the correct answer because it directly fulfills the requirement of session synchronization.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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