This article describes how to address Fortiguard when Anycast default method does not work.
For version 6.4.3 and above.
Per default FortiOS, 6.4.3 and above is using the Anycast method to address the Fortiguard servers.
Relying on Fortinet DNS servers, the FortiGate will get a single IP address for the domain name of each FortiGuard service.
In some circumstances Anycast does not work: