DNS

The DNS directive specifies whether the server performs DNS lookups on clients that access the server. When a client connects to your server, the server knows the client’s IP address but not its host name (for example, it knows the client as 198.95.251.30, rather than its host name www.a.com). The server will resolve the client’s IP address into a host name for operations like access control, CGI, JSP, Servlet, error reporting, and access logging.

If your server responds to many requests per day, you might want (or need) to stop host name resolution; doing so can reduce the load on the DNS or NIS (Network Information System) server.