| Description | This article describes the basic troubleshooting when a DNS rating error is encountered (no available FortiGuard SDNS servers). |
| Scope | FortiOS firmware 6.0 and above. |
| Solution |
SDNS servers are DNS servers used by DNS filter profiles. The DNS lookup requests will be sent to the FortiGuard DNS service and resolve end-user queries with an IP address and a domain rating that includes the FortiGuard category of the web page. The SDNS server IP address might be different depending on location.
The default FortiDNS server located in USA (IP address: 208.91.112.220), and the in the London server, UK (IP address: 194.69.172.53).
Follow the steps below the DNS rating error is appaearing (no available FortiGuard SDNS servers):
By default, FortiGate uses UDP port 53 to connect to the SDNS server.
1) Verify the connection between FortiGate and the SDNS server:
#diagnose test application dnsproxy 3
In this example, it is:
In the CLI Console:
# execute ping 208.91.112.220
Note. If VDOM is enabled, run the command under management VDOM.
2) Modify the FortiGuard setting through CLI console:
# config system fortiguard
The North American server should work in most cases. However, it is possible to switch to the European server (IP address: 194.69.172.53) to see if it improves latency.
This command can be used to check the DNS proxy status. Use '?' to list down the Test level.
# diagnose test application dnsproxy ?
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