FortiGate IPsec VPN Site to Site Configuration

FortiGate IPsec VPN Site to Site provides a secure and reliable connection between two networks located in different locations. This is a crucial feature for businesses with remote offices and a requirement for remote workers. In this blog post, we’ll discuss how to configure FortiGate IPsec VPN Site to Site and provide training on its usage.


  • Two FortiGate devices (FortiGate A and FortiGate B) with administrative access.
  • A dedicated public IP address for each FortiGate device.
  • Proper network routing configured on both FortiGate devices.

Step 1: Log in to the FortiGate Web Interface

  1. Open a web browser and enter the IP address of FortiGate A in the address bar.
  2. Log in with administrative credentials.

Step 2: Create Phase 1 Configuration on FortiGate A: Phase 1 sets up the initial connection between the two VPN peers.

  1. Go to “VPN” > “IPsec Wizard” on FortiGate A.
  2. Select “Custom” for the VPN Template.
  3. Configure the following Phase 1 settings:
    • Name: Give the VPN connection a name.
    • Remote Gateway: Enter the public IP address of FortiGate B.
    • Authentication Method: Pre-shared Key (PSK).
    • Pre-shared Key: Enter a strong, secret key.
    • Local Interface: Select the local interface connected to the internet.
    • Mode: Main Mode.
    • IKE Version: IKEv2 or IKEv1, depending on your requirements.
    • Phase 1 Proposal: Define encryption and authentication algorithms.
  4. Click “Next” to save the Phase 1 settings.

Step 3: Create Phase 2 Configuration on FortiGate A: Phase 2 defines the parameters for the actual data encryption.

  1. After saving Phase 1 settings, click “Next” to configure Phase 2.
  2. Configure the following Phase 2 settings:
    • Phase 2 Name: Give it a name.
    • Local Subnet: Enter the local network subnet behind FortiGate A.
    • Remote Subnet: Enter the remote network subnet behind FortiGate B.
    • P2 Proposal: Define encryption and authentication algorithms.
  3. Click “Next” to save the Phase 2 settings.

Step 4: Create Phase 1 and Phase 2 Configuration on FortiGate B: Repeat Steps 2 and 3 on FortiGate B with the corresponding settings, but make sure to reverse the “Remote Gateway” and the “Local Subnet” and “Remote Subnet” settings.

Step 5: Establish the Connection:

  1. After configuring both FortiGate devices, return to FortiGate A.
  2. Go to “VPN” > “IPsec Tunnels” and click the “Create New” button.
  3. Select the Phase 1 and Phase 2 configurations you created for FortiGate B.
  4. Click “OK” to create the VPN tunnel.
  5. Repeat the same steps on FortiGate B, using the Phase 1 and Phase 2 configurations for FortiGate A.

Step 6: Monitor and Troubleshoot:

  1. You can monitor the VPN connection status under “VPN” > “Monitor” > “IPsec Monitor.”
  2. If there are any issues, check the logs and firewall policies for any blocking rules.

That’s it! You should now have a functioning FortiGate IPsec VPN site-to-site connection between the two locations. Ensure that your firewall policies allow traffic to flow over the VPN tunnel, and test the connectivity between the remote networks.

Fortigate Multiple Interface Policy

“Welcome to my channel! In this video, I will describe how to configure firewall policies with multiple source and destination interfaces in FortiGate. We’ll be looking at how to allow traffic between multiple interfaces on your FortiGate firewall, which is particularly useful when you have different subnets that you want to control traffic between or when you have multiple VLANs that need to communicate with each other. By the end of this video, you’ll have a better understanding of how to configure these policies in FortiGate and how they can help secure your network.

  1. Network Interfaces:
    • In a FortiGate device, you typically have multiple network interfaces, each connected to a different network segment or zone. These interfaces can be physical (Ethernet ports) or virtual (VLANs, subinterfaces, loopback interfaces, etc.).
  2. Traffic Flow:
    • Traffic flows between these interfaces as data packets are transmitted through the FortiGate device. Each interface represents a different security zone, and traffic between these zones must be controlled and inspected for security purposes.
  3. Security Policies:
    • FortiGate uses security policies to determine how traffic is treated as it passes between these interfaces. Security policies are rules that define the permitted actions for specific types of traffic. They include criteria like source and destination IP addresses, ports, protocols, and more.
  4. Multiple Interface Policy:
    • The “Multiple Interface Policy” feature in FortiGate allows you to create a single security policy that applies to traffic flowing between multiple interfaces or zones. This is especially useful when you want to define a consistent policy for a specific category of traffic across multiple interfaces.
  5. Use Cases:
    • There are several use cases for Multiple Interface Policies:
      • DMZ Configuration: If you have a DMZ zone with multiple servers that need different levels of access, you can create a single policy to control traffic from different internal zones to the DMZ.
      • Guest Network Isolation: You can use this feature to control traffic from the guest network to multiple internal networks with a single policy.
      • VPN Traffic: When you have multiple VPN tunnels terminating on different interfaces, you can create a policy that applies to traffic from all those tunnels.
  6. Policy Configuration:
    • When configuring a Multiple Interface Policy, you define the policy’s source and destination interfaces (security zones), specify the criteria for matching traffic (source/destination addresses, services, users, etc.), and define the action to take (allow, deny, NAT, etc.).
  7. Policy Order:
    • Policy order is important. FortiGate processes policies from top to bottom, and the first matching policy is applied. So, you should order your Multiple Interface Policies appropriately to ensure that more specific policies are evaluated before broader ones.
  8. Logging and Monitoring:
    • FortiGate provides extensive logging and monitoring capabilities, allowing you to track traffic as it traverses the different interfaces and the policies applied to it.
  9. Traffic Inspection:
    • Depending on your policy settings, FortiGate can perform various security functions like antivirus scanning, intrusion detection and prevention, content filtering, and more on the traffic as it flows between interfaces.

In summary, FortiGate Multiple Interface Policies are a crucial part of network security configuration. They enable you to manage and secure traffic between multiple network interfaces by defining specific security policies that dictate how traffic should be handled. This feature is particularly useful in complex network environments with diverse security requirements.