DNS study notes — Records A/CNAME/NS/MX

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Introduction

In this post we will cover:

• Name server
• Zone
• Resource record

Name server and zone

Under DNS, each domain has a name server. The name server manages the following information.

• Correspondence between the host name directly below and its IP address
• Correspondence between subdomain and IP address of its name server

Information managed by the name server is called zone information. A domain can rewrite a part of the domain namespace by rewriting the name server. In other words, zone information can be said to be the range in which a domain has authority for the domain namespace . When identifying the IP of a host from the FQDN, query the domain name server starting from the root domain and ordering from the back to the front of the FQDN. If the name server goes down, you will not be able to make inquiries via DNS. Therefore, a domain usually has two or more name servers to improve fault tolerance. The client that queries the name server is called a resolver, and is usually provided as a function of the OS.

Resource records