Troubleshooting Tip: FortiGate is not using the configured DNS server

[hhasny]

Description	This article describes the use of DNS-server-override when the internet link is dynamic (PPPoE or DHCP).
Scope	FortiGate 6.4. FortiGate 7.0. FortiGate 7.2. FortiGate 7.4.
Solution	When the FortiGate internet is assigned an IP address from PPPoE or DHCP, it will get a DNS IP from it. FortiGate will use the acquired DNS IP for the ISP, as well as the configured DNS server IP in the DNS settings. To use the configured DNS server, disable the 'Override internal DNS'. This does not mean that FortiGate DNS will not be used. There are cases when acquired DNS from ISPs is not reachable or when system DNS has lower latency, in this case, both acquired and system DNS will be used. One example of implementing this feature is when using VDOMs and using specific DNS servers for a particular VDOM and not using global settings but per-vdom DNS. From CLI: config system interface     edit "<ISP>"         set dns-server-override enable    (by default)     next end Related documents: config system interface - FortiGate CLI reference. Configure interfaces - FortiGate CLI reference.