Howto setting-up IPsec-VPN between m0n0wall and FortiGatehere this approach to build an vpn tunnel to the fortigate unit
of course you can follow this screenshot will gather this link
http://www.a-enterprise.ch/content/view/235/97/in fortigate if anybody prefer insert into CLI
config vpn ipsec phase1
edit "AE-Net"
set interface "wan"
set nattraversal disable
set proposal 3des-sha1 3des-md5
set remote-gw 10.0.0.10
set psksecret ENC xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
next
end
config vpn ipsec phase2
edit "AE-Net10"
set pfs disable
set phase1name "AE-Net"
set proposal 3des-sha1 3des-md5
set dst-subnet 10.10.10.0 255.255.255.0
set src-subnet 192.168.1.0 255.255.255.0
next
end
config firewall policy
edit 2
set srcintf "internal"
set dstintf "wan"
set srcaddr "all"
set dstaddr "all"
set action ipsec
set schedule "always"
set service "ANY"
set inbound enable
set outbound enable
set vpntunnel "AE-Net"
next
end