Support Forum
The Forums are a place to find answers on a range of Fortinet products from peers and product experts.
New Contributor

How to get SD WAN to Volume Load-Balance for 2 WAN Connections and use a 3rd as FailOver



i want to configure my 3 WAN Connections in a way that 2 of them are Load Balanced by Volume / Sessions and a 3rd one as FailOver only if all other connections Fail. Is that possible?


I tried to set the Weights to 50 for WAN1, 20 for WAN2 (according to their Speed) and 0 for the third. But then the third Connection is also used with several MBit/s wich i want to prevent as this is a Volume Limited LTE Connection.


Any oder idea? Right now i use spillover, but i want to use both good WAN Connections equally. Thanks,



I don't think SDWAN/WLLB can do this alone.

you could create a volume based sdwan on the two WAN you want to be loadbalanced.

And then create one default route over the sdwan and a 2nd one (with higher prio/distance) using the third one.

Then traffic would primarily go to the loadbalancer and if that is unavailable will go to the thrid wan.


"It is a mistake to think you can solve any major problems just with potatoes." - Douglas Adams

-- "It is a mistake to think you can solve any major problems just with potatoes." - Douglas Adams
New Contributor

That sounds reasonable, i will try this configuration



New Contributor

I just tried this configuration - problem is that no second default Route pointing to is allowed by Fortigate.


Message is

You cannot have duplicated routes on SD-WAN and non SD-WAN interfaces.   I searched the forum but i only found some threads from users with the same problem but no solution...   If anybody has a good idea please let me know...    
New Contributor II

Hi Tobias,


You can use SD-WAN and change the priority to the third member, once you do that, the traffic will balance between the 2 members with lower priority and once the two of them fail, the third will kick in ... something like this


config system virtual-wan-link
    set status enable
    set load-balance-mode source-dest-ip-based
    config members
        edit 1
            set interface "port1"
            set gateway x.x.x.x
        edit 2
            set interface "port2"
            set gateway y.y.y.y
        edit 3
            set interface "port3"
            set gateway z.z.z.z
            set priority 4294967295
            set comment "Failover interface"


Hope it helps,




Select Forum Responses to become Knowledge Articles!

Select the “Nominate to Knowledge Base” button to recommend a forum post to become a knowledge article.

Top Kudoed Authors