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> Chapter 15 - IPsec VPN > IPsec VPN overview > Planning your VPN

Planning your VPN

It is a good idea to plan the VPN configuration ahead of time. This will save time later and help you configure your VPN correctly.

All VPN configurations are comprised of numerous required and optional parameters. Before you begin, you need to determine:

  • Where the IP traffic originates and where it needs to be delivered
  • Which hosts, servers, or networks to include in the VPN
  • Which VPN devices to include in the configuration
  • Through which interfaces the VPN devices communicate
  • Through which interfaces do private networks access the VPN gateways

Once you have this information, you can select a VPN topology that suits the network environment.

Network topologies

The topology of your network will determine how remote peers and clients connect to the VPN and how VPN traffic is routed.

VPN network topologies and brief descriptions
Topology Description
Gateway-to-gateway configurations Standard one-to-one VPN between two FortiGate units. See Gateway-to-gateway configurations on page 1.
Hub-and-spoke configurations One central FortiGate unit has multiple VPNs to other remote FortiGate units. See Hub-and-spoke configurations on page 1.
Dynamic DNS configuration One end of the VPN tunnel has a changing IP address and the other end must go to a dynamic DNS server for the current IP address before establishing a tunnel. See Dynamic DNS configuration on page 1.
FortiClient dialup-client configurations Typically remote FortiClient dialup-clients use dynamic IP addresses through NAT devices. The FortiGate unit acts as a dialup server allowing dialup VPN connections from multiple sources. See FortiClient dialup-client configurations on page 1.
FortiGate dialup-client configurations Similar to FortiClient dialup-client configurations but with more gateway-to-gateway settings such as unique user authentication for multiple users on a single VPN tunnel. See FortiGate dialup-client configurations on page 1.
Internet-browsing configuration Secure web browsing performed by dialup VPN clients, and/or hosts behind a remote VPN peer. See Internet-browsing configuration on page 1.
Redundant VPN configurations Options for supporting redundant and partially redundant IPsec VPNs, using route-based approaches. See Redundant VPN configurations on page 1.
Transparent mode VPNs In transparent mode, the FortiGate acts as a bridge with all incoming traffic being broadcast back out on all other interfaces. Routing and NAT must be performed on external routers. See Transparent mode VPNs on page 1.
L2TP and IPsec (Microsoft VPN) Configure VPN for Microsoft Windows dialup clients using the built in L2TP software. Users do not have to install any See L2TP and IPsec (Microsoft VPN) on page 1.

These sections contain high-level configuration guidelines with cross-references to detailed configuration procedures. If you need more detail to complete a step, select the cross-reference in the step to drill-down to more detail. Return to the original procedure to complete the procedure. For a general overview of how to configure a VPN, see Planning your VPN .