How to set/route different true IP (Fortigate 100E)

Dear All,

 

My ISP give us 2 different range of true IP address as below:

 

IP RANGE:       10.100.186.144  ~ 10.100.186.151    (8)  10.100.188.32   ~ 10.100.188.63     (32)    10.100.186.145       (TYPE: GATEWAY)  10.100.186.148       (TYPE: WAN IP)  10.100.186.151       (TYPE: BROADCAST)  10.100.188.32        (TYPE: ROUTER_NETWORK)  10.100.188.62        (TYPE: GATEWAY)  10.100.188.63        (TYPE: ROUTER_BROADCAST)    BB GATEWAY:  165.84.186.145 165.84.188.62   SUBNET:  255.255.255.224 255.255.255.248   I set WAN using 10.100.186.148 (gw:165.84.186.145)，10.100.188.xx added to WAN secondary address, and setting Virtual IP, I can open my webserver page my 10.100.188.xx and LAN is working properly.   However, I hope my new server connecting internet and show 10.100.188.xx (whatismyip.com), but it shows 10.100.186.148.  ISP told me I have to make static route instead of current settings.  I should keep the new server keep internal IP address (10.10.181.2), can any one help me?  Many thanks.   Ben