Oracle Network Administration - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 208

Figure 8-9: Dynamic Service Registration happen only if we use
default Listener Name, Protocol, Port. Two ways to do Dynamic
service registration namely, use the default listener or specify the
following three init.ora parameters LOCAL_LISTENER,
INSTANCE_NAME & SERVICE_NAMES
Select the listener name and click “Add Addresses” button on the
right pane of ONM. Once you click this button Oracle adds the
default values for Host (i.e. name of the machine running Oracle
Server or its IP address in case no name resolution service like
DNS is available), Protocol (i.e. TCP/IP) and port (i.e. 1521).