Partially-redundant route-based VPN example

Partiallyredundant route-based VPN example

This example demonstrates how to set up a partially redundant IPsec VPN between a local FortiGate unit and a remote VPN peer that receives a dynamic IP address from an ISP before it connects to the FortiGate unit. For more information about FortiGate dialup-client configurations, see FortiGate dialup-client configurations on page 1716.

When a FortiGate unit has more than one interface to the Internet (see FortiGate_1), you can configure redundant routes. If the primary connection fails, the FortiGate unit can establish a VPN using the redundant connection.

In this case, FortiGate_2 has only one connection to the Internet. If the link to the ISP were to go down, the connection to FortiGate_1 would be lost, and the tunnel would be taken down. The tunnel is said to be partially redundant because FortiGate_2 does not support a redundant connection.

In the configuration example:

  • Both FortiGate units operate in NAT mode.
  • Two separate interfaces to the Internet (192.168.10.2 and 172.16.20.2) are available on FortiGate_1. Each interface has a static public IP address.
  • FortiGate_2 has a single connection to the Internet and obtains a dynamic public IP address (for example, 172.16.30.1) when it connects to the Internet.
  • FortiGate_2 forwards IP packets from the SOHO network (10.31.101.0/24) to the corporate network (10.21.101.0/24) behind FortiGate_1 through a partially redundant IPsec VPN. Encrypted packets from FortiGate_2 are addressed to the public interface of FortiGate_1. Encrypted packets from FortiGate_1 are addressed to the public IP address of FortiGate_2.

 

There are two possible paths for communication between the two units. In this example, these paths, listed in descending priority, are:

  • FortiGate_1 WAN 1 to FortiGate_2 WAN 1
  • FortiGate_1 WAN 2 to FortiGate_2 WAN 1

For each path, VPN configuration, security policies and routing are defined. By specifying a different routing distance for each path, the paths are prioritized. A VPN tunnel is established on each path, but only the highest priority one is used. If the highest priority path goes down, the traffic is automatically routed over the next highest priority path. You could use dynamic routing, but to keep this example simple, static routing is used.

 

Example partially redundant route-based configuration

 

Configuring FortiGate_1

Whenconfiguring FortiGate_1, you must:

  • Configure the interfaces involved in the VPN.
  • Define the Phase 1 configuration for each of the two possible paths, creating a virtual IPsec interface for each one.
  • Define the Phase 2 configuration for each of the two possible paths.
  • Configure incoming and outgoing security policies between the internal interface and each of the virtual IPsec interfaces.

To configure the network interfaces

1. Go to Network > Interfaces.

2. Select the Internal interface and select Edit. Enter the following information and select OK:

Addressing mode                     Manual

IP/Netmask                                 10.21.101.2/255.255.255.0

3. Select the WAN1 interface and select Edit. Enter the following information and select OK:

Addressing mode                     Manual

IP/Netmask                                 192.168.10.2/255.255.255.0

4. Select the WAN2 interface and select Edit. Enter the following information and select OK:

Addressing mode                     Manual

IP/Netmask                                 172.16.20.2/255.255.255.0

 

To configure the IPsec interfaces (Phase 1 configurations)

1. Go to VPN > IPsec Tunnels and create the new custom tunnel or edit an existing tunnel.

2. Edit the Phase 1 Proposal (if it is not available, you may need to click the Convert to Custom Tunnel button).

3. Enter the following information, and select OK:

Name                                           Site_1_A

Remote Gateway                       Dialup User

Local Interface                          WAN1

Mode                                           Main

Authentication Method            Preshared Key

Preshared Key                          Enter the preshared key.

Peer Options                             Any peer ID

Advanced

Dead Peer Detection                 Select

4. Create a new tunnel and enter the following Phase 1 information:

Name                                           Site_1_B

Remote Gateway                       Dialup User

Local Interface                          WAN2

Mode                                           Main

Authentication Method            Preshared Key

Preshared Key                          Enter the preshared key.

Peer Options                             Any peer ID

Advanced

Dead Peer Detection                 Select

 

To define the Phase 2 configurations for the two VPNs

1. Open the Phase 2 Selectors panel.

2. Enter the following information and select OK:

Name                                           Route_A

Phase 1                                       Site_1_A

3. Enter the following Phase 2 information for the subsequent route:

Name                                           Route_B

Phase 1                                       Site_1_B

 

To configure routes

1. Go to Network > Static Routes.

2. Select Create New, enter the following default gateway information and select OK:

Destination IP/Mask                 0.0.0.0/0.0.0.0

Device                                         WAN1

Gateway                                     192.168.10.1

Distance (Advanced)                10

 

To configure security policies

1. Go to Policy & Objects > IPv4 Policy and select Create New.

2. Enter the following information, and select OK:

Incoming Interface                   Internal

Source Address                        All

Outgoing Interface                   Site_1_A

Destination Address                 All

Schedule                                    Always

Service                                       Any

Action                                         ACCEPT

3. Select Create New.

4. Enter the following information, and select OK:

Incoming Interface                   Internal

Source Address                        All

Outgoing Interface                   Site_1_B

Destination Address                 All

Schedule                                    Always

Service                                       Any

Action                                         ACCEPT

 

Configuring FortiGate_2

The configuration for FortiGate_2 is similar to that of FortiGate_1. You must

  • configure the interface involved in the VPN
  • define the Phase 1 configuration for the primary and redundant paths, creating a virtual IPsec interface for each one
  • define the Phase 2 configurations for the primary and redundant paths, defining the internal network as the source address so that FortiGate_1 can automatically configure routing
  • configure the routes for the two IPsec interfaces, assigning the appropriate priorities
  • configure security policies between the internal interface and each of the virtual IPsec interfaces

 

To configure the network interfaces

1. Go to Network > Interfaces.

2. Select the Internal interface and select Edit. Enter the following information and select OK:

Addressing mode                     Manual

IP/Netmask                                 10.31.101.2/255.255.255.0

3. Select the WAN1 interface and select Edit. Set the Addressing mode to DHCP.

 

To configure the two IPsec interfaces (Phase 1 configurations)

1. Go to VPN > IPsec Tunnels and create the new custom tunnel or edit an existing tunnel.

2. Edit the Phase 1 Proposal (if it is not available, you may need to click the Convert to Custom Tunnel button).

3. Enter the following information, and select OK:

Name                                           Site_2_A

Remote Gateway                       Static IP Address

IP Address                                 192.168.10.2

Local Interface                          WAN1

Mode                                           Main

Authentication Method            Preshared Key

Preshared Key                          Enter the preshared key.

Peer Options                             Any peer ID

Advanced

Dead Peer Detection                 Select

4. Create a new tunnel and enter the following Phase 1 information:

Name                                           Site_2_B

Remote Gateway                       Static IP Address

IP Address                                 172.16.20.2

Local Interface                          WAN1

Mode                                           Main

Authentication Method            Preshared Key

Preshared Key                          Enter the preshared key.

Peer Options                             Any peer ID

Advanced

Dead Peer Detection                 Select

 

To define the Phase 2 configurations for the two VPNs

1. Open the Phase 2 Selectors panel.

2. Enter the following information and select OK:

Name                                           Route_A

Phase 1                                       Site_2_A

Advanced

Source Address                        10.31.101.0/24

3. Enter the following Phase 2 information for the subsequent route:

Name                                           Route_B

Phase 1                                       Site_2_B

Advanced

Source Address                        10.31.101.0/24

 

To configure routes

1. Go to Network > Static Routes.

2. Select Create New, enter the following information and then select OK:

Destination IP/Mask                 10.21.101.0/255.255.255.0

Device                                        Site_2_A

Distance (Advanced)                1

3. Select Create New, enter the following information and then select OK:

Destination IP/Mask                 10.21.101.0/255.255.255.0

Device                                        Site_2_B

Distance (Advanced)                2

 

To configure security policies

1. Go to Policy & Objects > IPv4 Policy and select Create New.

2. Enter the following information, and select OK:

Incoming Interface                   Internal

Source Address                        All

Outgoing Interface                   Site_2_A

Destination Address                 All

Schedule                                    Always

Service                                       Any

Action                                         ACCEPT

3. Select Create New.

4. Enter the following information, and select OK:

Incoming Interface                   Internal

Source Address                        All

Outgoing Interface                   Site_2_B

Destination Address                 All

Schedule                                    Always

Service                                       Any

Action                                         ACCEPT

 

Creating a backup IPsec interface

You can configure a route-based VPN that acts as a backup facility to another VPN. It is used only while your main VPN is out of service. This is desirable when the redundant VPN uses a more expensive facility.

You can configure a backup IPsec interface only in the CLI. The backup feature works only on interfaces with static addresses that have dead peer detection enabled. The monitor option creates a backup VPN for the specified Phase 1 configuration.

In the following example, backup_vpn is a backup for main_vpn.

 

config vpn ipsec phase1-interface edit main_vpn

set dpd on

set interface port1

set nattraversal enable

set psksecret “hard-to-guess” set remote-gw 192.168.10.8

set type static end

edit backup_vpn set dpd on

set interface port2 set monitor main_vpn

set nattraversal enable

set psksecret “hard-to-guess” set remote-gw 192.168.10.8

set type static end


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