Disclosed is a network system and a control method thereof, the network system including a gateway connected to a plurality of home appliances through a home area network, an outdoor apparatus connected to the gateway through a network, and a dynamic domain name system (DDNS) server to manage dynamic internet protocol (IP) address information about an apparatus using a dynamic IP address. A communication connection is achieved through a dynamic IP between a gateway inside the home and an apparatus outside the home in a smart grid network environment, so a user can easily access in-home services based on a dynamic IP. In addition, unauthorized traffic, which may be introduced into the home, is automatically blocked, so that the quality of the home network service is improved.