I need your advise.
Our office HQ and 2 branches has using adsl broadband for internet connection.
Recently we want to link this 3 site using VPN.
The device we choose is Fortigate 80C for HQ and 50b for branches.
Currently we use Allied Telesis adsl router and TP-Link adsl router (has static Public IP assinged to the adsl router).
In all manual from Fortigate about VPN I read, it required to assigned Static Public IP to Fortigate.
In my case, the static Public IP already assigned at ADSL router.
I googling and there is some clue about NAT-T on ADSL router, Half Bridged on ADSL router, Port forwarding on 1732, Port forwarding on 500 UDP + 4500 UDP, etc ...
What should I do in order to bring VPN up for 3 sites with currently ADSL connection? How to setting ADSL router? Any extra setting required to Fortigate? Assume I follow manual guide from Fortinet, except Static Public IP.
Simple Network diagram:
AR: ADSL Router
Thank you very much in advance and sorry for my bad english.