Site to Site VPN - Fortigate

try this:
http://www.computing.net/answers/networking/site-to-site-vpn-with-2-lan-subnets/34629.html
from ee
https://www.experts-exchange.com/questions/21881945/about-site-to-site-VPN.html
https://www.experts-exchange.com/questions/22635563/Site-to-Site-to-Site-VPN's-and-fortinet.html

I believe that this problem is associated to a routing issue on the Site A firewall. When I try to ping any of the Site A devices I get "Destination Net Unreachable" and a tracert will not get passed the Site a firewall address. In the original question the Site A WAN address should read 72.xx.xx.174

Can you post some screen shots of your Policy setup and VPN config? Or just post your config with external IP's changed?

Have you followed this example?
http://kb.fortinet.com/kb/microsites/search.do?cmd=displayKC&docType=kc&externalId=FD30023&sliceId=1&docTypeID=DT_KCARTICLE_1_1&dialogID=5147783&stateId=0 0 5149062

I had that example that you provided a link to - the setup we have is similar and I double checked all the settings but still no luck. The Site B firewall seems to be unaware of the 192.168.58.0 subnet at the other end and that's why I'm getting the "Destination Net Unreachable" message on the ping commands. Tracert from Site B will only show the Site B router address and then fails.
I have attached the Address and Policy screen shots. Site A is Flycreek and Site B is RRCA. I believe that the tunnel setup is correct - we can ping the firewall at Site B from Site A. Thanks.
Address.jpg
Policy.jpg

I did what you suggested and now it's working fine. Thank you!