This really isn't a great table design since you're not actually gaining anything by splitting the information this way. The lookups are slower than on a single table using a straighforward SELECT query along the lines of "SELECT ipaddress WHERE name=?", but you haven't gained any additional flexibility since everything is bound to the name_id.,

If you really want to use ids to track this information a better schema would be:

create table names (
   name_id INT NOT NULL auto_increment,
   name_str VARCHAR(255)
   );

create table ipaddresses (
   ipaddress_id INT NOT NULL auto_increment,
   ipaddress_value VARCHAT(255)
   );

create table ip_names (
   name_id INT NOT NULL,
   ipaddress_id INT NOT NULL
   );
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This gives you a lot more flexibility -- reverse look ups on virtual hosts, for instance, and allows for extensibility at a later date (associating machine-specific information with an IP address id, and domain specific information with the name id).