Technical Tip: FortiGuard is not reachable via Anycast default method

[vvarangoulis]

Description

This article describes how to address Fortiguard when Anycast default method does not work.

Scope

For version 6.4.3 and above.

Solution

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:

This can be verified with the debug command 'diagnose debug rating':

diagnose debug rating

Locale       : english

Service      : Web-filter

Status       : Enable

License      : Contract 

Service      : Antispam

Status       : Disable 

Service      : Virus Outbreak Prevention

Status       : Disable 

Num. of servers : 1

Protocol        : https

Port            : 443

Anycast         : Enable

Default servers : Included

-=- Server List (Tue Nov  3 17:47:32 2020) -=-

 IP                                             Weight    RTT Flags   TZ    Packets  Curr Lost Total Lost             Updated Time

173.243.140.16                                      0      0 DIF      0         14         11         11

If a high value of the current loss is noticed, run 'execute traceroute X.X.X.X' to see if the FortiGuard server can be reached (while X.X.X.X is the failing IP of 'diagnose debug rating').

If the Server cannot be reached, choose between the following options to workaround this issue:

1. Switch to other Anycast servers:

config system fortiguard                                   
    set fortiguard-anycast-source aws                           
end                         

2. Disable Anycast and use HTTPS with port 8888.
   config system fortiguard
       set fortiguard-anycast disable
       set protocol https 
       set port 8888

       set sdns-server-ip 208.91.112.220

   end
3. Disable Anycast and use UDP with Port 53.
   config system fortiguard
       set fortiguard-anycast disable
       set protocol udp
       set port 53
       set sdns-server-ip 208.91.112.220
   end

4. Disable Anycast and use UDP with Port 8888.
   
   

   config system fortiguard
       set fortiguard-anycast disable
       set protocol udp
       set port 8888
       set sdns-server-ip 208.91.112.220
   end

Note: This article's contents mainly pertains to the newer anycast method for FortiGuard communications. For legacy deployments, anycast is not available. To troubleshoot without anycast, refer to this article:

Troubleshooting Tip: Resolving FDS Communication Issues (FortiGuard Distribution Servers)