Server_Name redirecting to IP

Hello,

Trying to figure out why when using a DNS entry for the "server_name" entry in the nginx/sites-available/ configuration files, it will still resolve an IP address in the web browser instead of serving up a 404?

This doesn't happen in any of my other environments which are set up the same way. Security audits say our production level webpage should never resolve to an IP Address. Only a DNS name.

Any thoughts of where I should start looking even, would be greatly appreciated.

~S