ImPossible to use Fortigate as Load Balancer ? - Two ISP VirtualIP to same Internal server

Hi all,

I know Fortigate supports LB for single ISP to multiple Web servers... No need to tell me again. I don't want this.

I am studying Fortigate 6.0.6, DNAT and SDWAN whether able to perform the inbound traffic load balancing over two ISPs.

Let have a look at my Virtual IP configurations:

edit "Test1"
 set extintf "wan1"
 set portforward enable
 set mappedip "192.168.1.106"
 set extport 80
 set mappedport 80
 next

edit "Test2"
set extintf "wan2"
set portforward enable
set mappedip "192.168.1.106"
set extport 80
set mappedport 80
next

Both Wan1 and 2 are DHCP with external DDNS working well.

And are in SDWAN group already:

config system virtual-wan-link set status enable set load-balance-mode source-dest-ip-based config members edit 1 set interface "wan1" next edit 2 set interface "wan2" next end

Well, then I run a test from the Internet to wan2 to trigger the incoming traffic.

I find that about 50% chance the incoming does come from wan2, but the return traffic is to wan1.....

Or, Vice Versa.

The dia sni pac any "host MyTestDeviceSrcIpFromInternetToMyWan2" does appear:

Wan2 in : MyTestDeviceSrcIpFromInternetToMyWan2 -> Wan2:80

DMZ Out : MyTestDeviceSrcIpFromInternetToMyWan2 -> 192.168.1.106:80

DMZ In : 192.168.1.106:80 -> MyTestDeviceSrcIpFromInternetToMyWan2 Wan1 Out : Wan2 Interface IP as Src IP :80 -> MyTestDeviceSrcIpFromInternetToMyWan2  Obviously wrong route interface in the final step .... How does my Wan1 ISP accept the Wan2 Src IP traffic?

Of course not and get a drop!

The only way for me to make it able to in/out from wan2 is to have a SDWAN rule to force the server use WAN2. But this just stop me using the Wan1 for the same server incoming traffic at the same time.

Any solution?