Site-to-site IPsec VPN with two FortiGates

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In this example, you will allow transparent communication between two networks that are located behind different FortiGates at different offices using route-based IPsec VPN. The VPN will be created on both FortiGates by using the VPN Wizard’s Site to Site FortiGate template.

In this example, one office will be referred to as HQ and the other will be referred to as Branch.

 

Find this recipe for other FortiOS versions
5.2 | 5.4 | 5.6 | 6.0

1. Configuring the HQ IPsec VPN

On the HQ FortiGate, go to VPN > IPsec > Wizard and select Site to Site – FortiGate.

In the Authentication step, set the Branch FortiGate’s IP as the Remote Gateway (in the example, 172.20.120.142). After you enter the gateway, an available interface will be assigned as the Outgoing Interface. If you wish to use a different interface, select Change.

Set a secure Pre-shared Key

In the Policy & Routing section, set Local Interface to your lan interface. The Local Subnet will be added automatically. Set Remote Subnets to the Branch FortiGate’s local subnet (in the example, 192.168.50.0/24).

A summary page shows the configuration created by the wizard, including firewall addresses, firewall address groups, a static route, and security policies.

2. Configuring the Branch IPsec VPN

On the Branch FortiGate, go to VPN > IPsec > Wizard and select Site to Site – FortiGate.

In the Authentication step, set the HQ FortiGate’s IP as the Remote Gateway (in the example, 172.20.120.123). After you enter the gateway, an available interface will be assigned as the Outgoing Interface. If you wish to use a different interface, select Change.

Set the same Pre-shared Key that was used for HQ’s VPN.

In the Policy & Routing section, set Local Interface to your lan interface. The Local Subnet will be added automatically. Set Remote Subnets to the HQ FortiGate’s local subnet (in the example, 192.168.100.0/24).

A summary page shows the configuration created by the wizard, including firewall addresses, firewall address groups, a static route, and security policies.

3. Results

A user on either of the office networks should be able to connect to any address on the other office network transparently.

If you need to generate traffic to test the connection, ping the Branch FortiGate’s internal interface from the HQ’s internal network.

Go to VPN > Monitor > IPsec Monitor to verify the status of the VPN tunnel. Ensure that its Status is Up and that traffic is flowing.

 

For further reading, check out Gateway-to-gateway configurations in the FortiOS 5.2 Handbook.

Victoria Martin

Victoria Martin

Technical Writer at Fortinet
Victoria Martin works in Ottawa as part of the FortiOS technical documentation team. She graduated with a Bachelor's degree from Mount Allison University, after which she attended Humber College's book publishing program, followed by the more practical technical writing program at Algonquin College. She does need glasses but also likes wearing them, since glasses make you look smarter.
Victoria Martin

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