What are the types of domain name server, which are mainly divided into the main domain server, including all host names and corresponding IP addresses in the region, as well as some information about the area. The auxiliary domain server contains a copy of the database of the area, providing information in the area like the main domain server. Caching only domain name server does not provide any authoritative information about the area, usually established to reduce the transmission of DNS.

　　1. Main domain server

　　Each DNS domain must have a main domain server. The main domain server includes all the host names in the region and its corresponding IP address, as well as some information about the area. The main domain server can use the information in the area to answer the client's inquiry. It usually needs to obtain the required information by asking other domain name servers. The information of the main domain server is stored in the form of resource records.

　　2. Auxiliary domain server

　　For the redundancy of information, there are at least one auxiliary domain name server in each domain. Each auxiliary domain name server contains a copy of the area data. Auxiliary domain name server provides area information like the main domain server. In response to the user's request, the auxiliary domain name server usually needs to ask other servers to get the information they want. Similar to the main domain server, there is also a cache in the auxiliary domain name server to save information obtained from other servers.

　　3. Caching only domain name server

　　The Caching only server does not provide any authoritative information about the area. When the user asked it, it only forwarded to other domain name servers until the answer was obtained, and the answer was saved in their own cache for a period of time. If the customer issued the same inquiries At the same time, it directly answers the information in cache, without asking for conversion to other domain name servers. Caching only domain name server is usually established to reduce the transmission of DNS.