config dns

Description: Configure DNS settings used to resolve domain names to IP addresses.

config system dns
  set primary {ipv4-address}
  set secondary {ipv4-address}
  set ip6-primary {ipv6-address}
  set ip6-secondary {ipv6-address}
  set timeout [1 – 10]
  set retry [0 – 5]
  set dns-cache-limit [0 – 4294967295]
  set dns-cache-ttl [60 – 86400]
  set cache-notfound-response [enable | disable]
  set source-ip {ipv4-address}
  set server-select-method [least-rtt | failover]
  unset
  show
end

Sample command:

config system dns
  set primary 208.91.112.53
  set secondary 208.91.112.52
  set ip6-primary 2001:4860:4860::8888
  set ip6-secondary 2001:4860:4860::8844
  set timeout 5
  set retry 3
  set dns-cache-limit 5000
  set dns-cache-ttl 1800
  set cache-Tonotfound-responses disable
  set source-ip 0.0.0.0
  set server-select-method least-rtt
end

Parameter	Description	Type	Size	Default
primary	Primary static DNS server IPv4 address. The default is the FortiGuard primary DNS server IP.	IPv4 address	-	208.91.112.53
secondary	Secondary static DNS server IPv4 address. The default is the FortiGuard secondary DNS server.	IPv4 address	-	208.91.112.52
ip6-primary	Primary static DNS server IPv6 address. The default value is empty and will not add to the DNS server pool.	IPv6 address	-	::
ip6-secondary	Secondary static DNS server IPv6 address. The default value is empty and will not add to the DNS server pool.	IPv6 address	-	::
timeout	DNS query timeout interval in seconds.	integer	1 - 10	5
retry	Specify the number of retry attempts allowed for unsuccessful connections.	integer	0 - 5	3
dns-cache-limit	Specify the maximum amount of records in the DNS cache that can be stored.	integer	0 - 4294967295	5000
dns-cache-ttl	Duration in seconds that DNS cache retains information.	integer	60 - 86400	1800
cache-notfound-responses	Specify whether or not to save the not-found response into cache. If enabled, no need to forward the not-found response to the DNS server in the future.	option	-	disable
	Option Description enable Enable cache-notfound-responses. disable Disable cache-notfound-responses.
source-ip	IP address used by the DNS server as its source IP.	IPv4 address	-	0.0.0.0
server-select-method	Specify how configured servers are prioritized.	option	-	least-rtt
	Option Descrption least-rtt In the dns-server selection pool, the round-trip time of each dns-server ip is calculated and sorted from the shortest to the longest, picking from the shortest one. failover This algorithm is a relatively fixed order. The first pick doesn't change until it fails the first time. The order is primary DNS > secondary DNS > dynamic DNS (learned from DHCP).