Hi @40mb,   I agree with @DarrenOC, if you are making changes on the MX WAN interface for its management DNS servers it should not affect clients' DNS. Keep in mind that, if you have your DHCP scope set to Proxy to upstream DNS, clients with existing DHCP lease will get the updated DNS server when they renew their lease and new clients will get updated DNS servers immediately with the new lease.     ... View more