Want to change default DNS for the network in MikroTik’s RouterOS CLI? You can use web UI but it could have some issues preventing from configuration save, so it is nice to know how to use it via CLI. First login into the box and then:

ip dhcp-server network set dns-server=1.1.1.1 X

Change X with the network number of your preference. You can show them using print command at /ip/dhcp-server/network level. Last thing: the option that may prevent from configuration save on UI is DHCP Option Set. When empty (for various reasons) then you need to go to CLI to do the job. It is the only way.