This setting specifies whether the server performs DNS (domain name service) lookups on clients that access the server. When DNS lookup is not enabled, when a client connects, the server knows the client’s IP address but not its host name (for example, it knows the client as 188.8.131.52, rather than www.xyz.com). When DS lookup is enabled, the server will resolve the client’s IP address into a host name for operations like access control, common gateway interface (CGI) programs, error reporting, and access logging.
If the server responds to many requests per day, reduce the load on the DNS or NIS (Network Information System) server by disabling DNS lookup. Enabling DNS lookup will increase the latency and load on the system—do so with caution.