Hi,
I just want to tell my story regarding my tests with a 3G wireless USB modem.
Hardware: FG50B
FortiOS: 4.00 MR2 Beta 2
3G Modem: Huwei E220
after hours of testing and failing i finally got it to work, beautiful !
I configured it for Redundant mode against WAN1, so when the internet failed on WAN1, the 3G modem automaticly dialed up my 3G ISP and added itself to the router list and i had a few seconds while it failed over to my Modem interface.
Here are some configs that made it work:
# config system modem
# set status enabled
# set mode redundant
# set idle-time 1
# set dial-on-demand enabled
# set interface WAN1
# set extra-initz1 " at+cgdcont=1," IP" ," internet.telenor.se" " (internet.telenor.se should be the APN for your service provider)
# set distance 100
# end
# config router static
# set device modem
# set dynamic-gateway enabled
# set distance 11
# end
create the appropiated firewall rules:
internal -> Modem (NAT enabled)
edit your wan1 interface
and fill out the " Detect Server" with an IP on the other side of your internet connection.
Hope this could help someone 
