The first command is ip domain-lookup, which is turned on by default. It needs to be entered
only if you previously turned it off (with the no ip domain-lookup command). The command
can be used without the hyphen as well (ip domain lookup).
The second command is ip name-server. This sets the IP address of the DNS server. You can
enter the IP addresses of up to six servers.
The last command is ip domain-name. Although this command is optional, it really should be
set. It appends the domain name to the hostname you type in. Since DNS uses a FQDN
system, you must have a full DNS name, in the form domain.com.