The ip domain lookup command configures the device to use DNS for hostname resolution. It must be accompanied by a command that specifies the location of the DNS server, which is done with the ip name-server command.

The ip dns-primary command is used to configure the device as the primary DNS name server for a domain (zone) and as the start of authority (SOA) record source, which designates the start of a zone.

The ip dns server command is used to make the device a DNS server.