When to use define('DB_HOST', 'localhost');

Good Day,

I just have a quick question…how do you know when to use define(‘DB_HOST’, ‘localhost’); over using an IP address (outside of when one doesn’t work try the other and creating a local install)?

I’ve had instances where I had 2 multisites installed on the same server where one needed the DB_HOST set to localhost in order to work and the other was fine with an IP address.

Thanks in advance!!!