An abbreviation for Domain Name System, DNS is a system employed for naming computers and network services. This system is organized into a hierarchical scheme of domains. Naming service provided by DNS is used in TCP/IP networks, such as the Internet, to easily locate computers and services like mail exchanger servers, through user-friendly names. When a user enters a DNS name in an application, DNS services resolves this name to other information associated with the name, such as an IP address. This paper presents the evaluation of a DNS server performance in the experimental backgrounds to establish the fact that frequent caching of results will improve the response time of the queries. It also simulates the client - server DNS model on OPNET.