wan-load-balancing - SNAT issue

[hklb]

Hi,

I have a wan-load-balancing with two ISP. in my exemple :

1.1.1.1/24, WAN1

2.2.2.1/24, WAN2

I have some VIP with the nat-source-vip enable. for exemple :

- 1.1.1.10 -> 10.10.1.10

My issue is if my server use the ISP WAN2, the fortigate do SNAT with IP 1.1.1.10 (instead of 2.2.2.1).

I already try to specify the "extintf" parameters in VIP configuration, but it's the same issue. The firmware is 5.2.7.

Do you have the same experience ? How can I fix this issue ?