VPN security policies

This section explains how to specify the source and destination IP addresses of traffic transmitted through an IPsec VPN, and how to define appropriate security policies.

Topology

Defining policy addresses

In a gateway-to-gateway, hub-and-spoke, dynamic DNS, redundant tunnel, or transparent configuration, you need to define a policy address for the private IP address of the network behind the remote VPN peer (for example, 192.168.10.0/255.255.255.0 or 192.168.10.0/24).

In a peer-to-peer configuration, you need to define a policy address for the private IP address of a server or host behind the remote VPN peer (for example, 172.16.5.1/255.255.255.255, 172.16.5.1/32, or 172.16.5.1).

For a FortiGate dialup server in a dialup-client or internet-browsing configuration, the source IP should reflect the IP addresses of the dialup clients:

Defining security policies

Policy-based and route-based VPNs require different security policies.

  • A policy-based VPN requires an IPsec policy. You specify the interface to the private network, the interface to the remote peer and the VPN tunnel. A single policy can enable traffic inbound, outbound, or in both directions.
  • A route-based VPN requires an accept policy for each direction. For the source and destination interfaces, you specify the interface to the private network and the virtual IPsec interface (phase 1 configuration) of the VPN. The IPsec interface is the destination interface for the outbound policy and the source interface for the inbound policy. One security policy must be configured for each direction of each VPN interface.
Note

If the policy that grants the VPN connection is limited to certain services, DHCP must be included, otherwise the client will not be able to retrieve a lease from the FortiGate’s (IPsec) DHCP server because the DHCP request (coming out of the tunnel) will be blocked.

Policy-based VPN

An IPsec policy enables the transmission and reception of encrypted packets, specifies the permitted direction of VPN traffic, and selects the VPN tunnel. In most cases, a single policy is needed to control both inbound and outbound IP traffic through a VPN tunnel. For a detailed example, see Policy-based IPsec tunnel. Be aware of the following before creating an IPsec policy.

Allow traffic to be initiated from the remote site

Policies specify which IP addresses can initiate a tunnel. By defaul