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SD-WAN on FortiGate (5.6)

SD-WAN became very popular topic in recent months. Many vendors have developed their own solution - including Fortinet. You can configure SD-WAN starting from version 5.6. The solution is totally free, it doesn't require any additional license. It is also available on 6.0 and 6.2 but there are some differences in functionality and configuration steps. I will cover them in a separate post.

Before we jump to the configuration steps I'd like to be sure you understand the concept of SD-WAN. The main goal is to have the ability to load-balance or just send specific type traffic using a specific path.  It sounds similar to what you can achieve by using Equal Cost Multipath (ECMP) and policy-based routing (PBR). SD-WAN gives you something else - the ability to the perform load balancing by checking following three parameters: packet loss, jitter and delay. 

Let's' get started with version 5.6 and in this post I'll describe configuration steps for SD-WAN with two IPsec tunnels. You can select normal WAN interfaces like Internet or MPLS, but one participant of my last NSE4 course asked me to show him the configuration steps with IPsec VPN. 

Assume you received following requirements from your customer:

- there are two servers in 2 locations: "local" -10.0.1.10 and "remote" - 10.0.2.10
- there are two IPsec tunnels vpn1 and vpn2
- traffic ICMP should be sent via vpn1
- traffic HTTP should be sent via the better tunnel, by comparing latency on vpn1 and vpn2 








Let's start from VPN - we need two tunnels on both FortiGates. You can use a template, which is available with the wizard.

FG1:


FG2:



When you setup the VPN using the wizard, firewall policies and static routes are already pre-configured for you.

FG1:

 

 

FG2:

 


Before we move to the next step make sure two VPNs work fine. It will be easier to find a problem when the config is simple.

Now it's time to add a new SD-WAN interface. It's a virtual interface, like a zone, with members. The minimum number of interfaces you can add is 2: vpn1 and vpn2 is my case. Default load balancing method is a 'source IP' but you can change it.




 


On FortiGates you can configure one SD-WAN interface per device/VDOM.

In the next step we have to define a server which we want to monitor: 10.0.1.10 from the FG2/Remote and 10.0.2.10 from the FG1 (Local). The check (packets) has to be sent via VPN:


 

Then we add rules where we specify how we want to distribute the traffic. According to the 'customer requirement we need: ICMP via vpn1 and TCP via both, preferring the be VPN with lower latency:







 In the next step we have to add a new static route:


 
 and firewall policies from, and to the server:




and remember to pu the policies in the correct order. I need to move them up, above the original VPN's ones:




To be able to monitor servers you need IP addresses on the VPN tunnel. A packet is sent from the FortiGate and without IP on the tunnel, the remote peer receives the packet with a public source address (VPN peer IP). The response packet would be sent via WAN interface, not VPN. IP address on the tunnel solves this problem. You can configure it via the CLI and the GUI:


…
edit "vpn1"
        set vdom "root"
        set ip 10.100.2.1 255.255.255.255
        set allowaccess ping
        set type tunnel
        set remote-ip 10.100.2.2 255.255.255.255
        set role wan
        set snmp-index 12
        set interface "port2"
    next
    edit "vpn2"
        set vdom "root"
        set ip 10.100.3.1 255.255.255.255
        set allowaccess ping
        set type tunnel
        set remote-ip 10.100.3.2 255.255.255.255
        set role wan
        set snmp-index 13
        set interface "port1"
    next
end

Local-FortiGate #


Remote-FortiGate #
…
edit "vpn1"
        set vdom "root"
        set ip 10.100.2.2 255.255.255.255
        set allowaccess ping
        set type tunnel
        set remote-ip 10.100.2.1 255.255.255.255
        set role wan
        set snmp-index 12
        set interface "port5"
    next
    edit "vpn2"
        set vdom "root"
        set ip 10.100.3.2 255.255.255.255
        set allowaccess ping
        set type tunnel
        set remote-ip 10.100.3.1 255.255.255.255
        set role wan
        set snmp-index 13
        set interface "port4"
    next
end

Remote-FortiGate #



I have to add a new policy to accept packets with source IP of the VPN tunnel (for the monitoring purpose):







This is how we see the quality of the VPN link (packet loss, latency and jitter):





Finally we can test it. ICMP is sent via vpn1 and HTTP via vpn2:

FG1:


 

FG2:

In the moment when I tested connection from FG2 (remote), latency on the vpn2 was higher than the vpn1. That's why all traffic is sent via (better) vpn1:


 
 
I think based on the above example you will be able to configure SD-WAN on your FortiGate. Let me know if you need any additional information. In the next post I'll show the differences between version 5.6 and 6.0. Stay tuned! 




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