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IPsec VPN overview

This section provides a brief overview of IPsec technology and includes general information about how to configure IPsec VPNs using this guide.

The following topics are included in this section:


VPN configurations interact with the firewall component of the FortiGate unit. There must be a security policy in place to permit traffic to pass between the private network and the VPN tunnel.

Security policies for VPNs specify:

  • The FortiGate interface that provides the physical connection to the remote VPN gateway, usually an interface connected to the Internet
  • The FortiGate interface that connects to the private network
  • IP addresses associated with data that has to be encrypted and decrypted
  • Optionally, a schedule that restricts when the VPN can operate
  • Optionally, the services (types of data) that can be sent

When the first packet of data that meets all of the conditions of the security policy arrives at the FortiGate unit, a VPN tunnel may be initiated and the encryption or decryption of data is performed automatically afterward. For more information, see Defining VPN security policies on page 1.

Where possible, you should create route-based VPNs. Generally, route-based VPNs are more flexible and easier to configure than policy-based VPNs — by default they are treated as interfaces. However, these two VPN types have different requirements that limit where they can be used.