Set DNS suffix in Fortigate
After sign in to Fortigate SSL VPN, user unable to access to local sites, unable to RDP to server or accessing network drive. When try to run ping to the FQDN, it will show could not find the host. However, if try to ping with suffix ad.local, it will be able to access.
After searching for quite sometime, I found an article show how to enter the dns suffix via CLI. For my case, it works as below.
Set DNS search suffix using CLI
config vpn ssl settings
set dns-suffix ad.local
Set Client DNS Server in the GUI
Navigate to VPN –> SSL –> Settings –> Tunnel Mode Client Settings. Specify the DNS Server setting and enter the IP addresses of your corporate DNS servers.
Finally it works.