Using the command line interface (CLI) : show : show system dns
 
show system dns
The show system dns command allows you to display the change of the DNS server addresses.
Syntax
show system dns
Example
The following is an example of the result of the show system dns command;
FD-XXX # show system dns
config system dns
set primary 65.39.139.53
set secondary 65.39.139.63
end
See also
config system dns