Simple definition
FortiGate is Fortinet’s firewall platform running FortiOS to secure, filter, and route network traffic.
Technical definition
A FortiGate combines stateful firewalling, routing, NAT, and VPN capabilities and, depending on the model, licensing, and configuration, advanced inspection and security features. Traffic is processed according to interfaces, routing, firewall policies, translation, and the security profiles that apply.
How it works / role
Its role is to control communication between network zones and the Internet, establish VPN tunnels, enforce access rules, and provide a central point for network visibility and security.
What is it used for?
Protect a site, segment VLANs, connect branches through VPN, publish services, control Internet access, or participate in an SD-WAN design.
Practical example
A company places a FortiGate between its LAN and the Internet. User and server VLANs use separate policies, outbound traffic is NATed, and branch offices connect through IPsec tunnels.
Common issues
- Missing firewall policy or incorrect policy order
- Incorrect route or interface
- Misconfigured NAT or address object
- Security inspection blocks or alters legitimate traffic
Related terms
FortiOS · Policy firewall FortiGate · SSL VPN FortiGate
Key takeaway: A useful FortiGate diagnosis follows the actual packet path: ingress interface, routing, firewall policy, NAT, security inspection, and egress interface.