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SD-WAN on FortiGate (6.2)

SD-WAN is very hot topic and as you may know the functionality is available on FortiGate platform for free. There are huge differences between versions as new features are added or modified. You need to check documentation for a particular version as sometimes the object names are different. The post is valid for version 6.2. 

I already published one post about the same topic but it was for version 5.6. Since then, adding VPN has changed and I would like to show the main differences.

As per below diagram, we have 2 sites with 2 FortiGate firewalls: FGT1 and FGT2. There are two servers on the left site:

- Linux - 10.0.1.20 (ssh)

- Windows - 10.0.1.10 (http)


There is a requirement to separate traffic to these two servers, but in case of any service degradation or failures, we can use all available links.

 

We start by enabling SD-WAN (remember - you can have 1 SD-WAN interface per device/VDOM!):

 


 Click "+Create New" and then select "+VPN":

 

 

You do not need to pre-define VPN tunnel. You can create it from the SD-WAN wizard. Provide the public IP address of the remote site and rest of the phase 1 details:

 


 Click OK and then "Close":

 

  
 
You can notice the new interface appears at the bottom of the list:
 
 

 
 
 
Once you select it, the first step is completed:
 
 


The first VPN interface is now part of the SD-WAN.



Repeat the same step and create the vpn2:

 


 

And now we have SD-WAN interface ready:

 


You need to repeat the same steps on the FGT2:

 


Now it is time to define SD-WAN Performance SLA for the Windows server for the HTTP traffic:


Repeat the same step for Linux server. Once you finish you can notice the FGT2 is not able to reach any of these servers. The traffic is initiated from FGT2 and it should be sent via VPN to the FGT1 and then to the final destination. 

The problem is, FGT2 is not able to send the monitoring packets to the tunnel without proper routing. You can't set the correct routing as long as the VPN interfaces do not have IP assigned.



Let's fix it:






Once all VPN have IP addresses we can perform a test:



Good, we can reach every IP address assigned to the VPN tunnel.


In the next step we can add a static route on the FGT2:




Now we can see stats for both servers:




In the next step we add a rule for the Linux server where we specify what type of traffic should be sent via which interface:





For Linux server we want "Best Quality", what means the FGT2 will switch the the 2nd interface if the primary one quality will be worse (by 10%, even if SLA is met). With this option you can notice more failovers.


The second rule we create for the Windows:


 

with the SLA target defined earlier. Maximize Bandwidth (SLA) can load balance traffic between interfaces, which satisfy SLA requirements:




In the next step we add firewall polices on both FortiGates:

FGT1:

FGT2:


We can start testing and you can see HTTP traffic to Windows server was sent via vpn2 (as per definition):



In the Events you can monitor all changes in the link preferences:



View: Network->Performance SLA:



From: Moitor->SD-WAN Monitor you can see how the sessions are load balanced between available SD-WAN members:



As you can see the configuration is straightforward. You don't need to configure the VPN before starting SD-WAN definition. You can also add a "normal" WAN interface and by using rules, define how the traffic should be distributed.






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